Font managing apparatus for a character generator

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a font managing apparatus for a character generator in which plural font pattern data are stored.

2. Description of Prior Art

Conventionally, the character generator of bit map type has been well known. In the character generator of bit map type, each character is formed as a bit image on a bit map memory according to font pattern data stored in a font memory. In a character generator of bit map type, fonts of several kinds are selectably stored in the font memory. In order to increase the number of selectable fonts, interchangeable font cartridges each of which has a ROM or character generator together with a command for designating a font. The character generator transforms each of transmitted code data into a bit image consulting with pattern data of the designated font. Bit images thus formed are sent to a printer and, thereby, the document is printed out in accordance with the designated font.

In a character generator which provides a variety of interchangeable font cartridges, an area for registering management information of individual fonts is provided for managing available fonts in a system RAM. Upon starting the character generator or when one or more font cartridges are interchanged, respective management information of available fonts is registered or renewed into the font managing area of the system RAM.

As a memory for memorizing font data which is provided in a font cartridge, a rewritable RAM is used other than a ROM. As a rewritable RAM, a RAM backed up with a back up power source is desirably used to hold font data even when the character generator is turned off. The RAM of this type has an external by operable input switch and font data is considered to be loaded down thereinto from the host computer as far as the external input switch is switched on.

If the switch is switched off or in the case of a font RAM which does not provide a back up power source, font data can be loaded down thereinto from the host computer.

In a character generator wherein plural font cartridges are settable and interchangeable, there is a possibility such that the font cartridge presently selected is drawn out or moved to another slot even when editing operation of character images is executed.

In such a case, it becomes necessary to reselect a font to be used.

Conventionally, when the font cartridge in use is drawn out, a font cartridge set in the slot adjacent to that of the drawn out font cartridge is selected automatically. However, if the font is reselected in this way, the font is changed one to another on the way of printing and this worsens quality of print.

In another conventional character generator, the operation thereof is automatically stopped as an error when the font cartridge in use is drawn out. In this case, it becomes necessary to load down font data again in order to start the suspended printing operation. Upon loading down font data, if a command for selecting a font contained in neither of font cartridges having been set is entered, it is processed as an error which urges to cancel it.

In the character generator of this type, a font is designated by appointing a slot number or a font name. Accordingly, it becomes necessary for an operator to have a preliminary knowledge of the slot number or font name regarding the desired font. However, it is difficult to designate the desired font exactly since each font is defined by attributes of font such as font name, pitch (print width), point (height of character), weight (print thickness) and the like which are unfamiliar to an ordinary user. This invites miss operation often.

In a font memory contained in a font cartridge, directory of font data which includes address information with respect to font patterns corresponding to character codes is also stored. Upon accessing the font memory, address information of a font pattern corresponding to a character code sent from the host computer is read out from the directory at first and, thereafter, the font pattern designated by the address information is read out. Accordingly, it is always needed to access the directory of the font memory every character. This access operation is done parallel to imaging operation of characters and, therefore, access time becomes long. This fairly limits the processing time.

In JP-A 116551/1986, there is disclosed a font managing system wherein address information of directories of individual font memories is stored as a directory address table in a system RAM in order to manage directories. Upon accessing a font pattern, the directory address table is accessed at first and, then, the corresponding font pattern stored in the font memory is read out.

If the memory area to be assigned to the directory address table is reasonably narrow so as to shorten the addressing time, character imaging operation can be executed at a high speed.

However, in JP-A 116551/1986, directories of all available fonts are registered in the directory address table of the system RAM. Due to this, the system RAM must have a large volume.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a font managing apparatus for a character generator having selectable fonts which is able to maintain quality of print as fine as possible even when it becomes necessary to reselect a font in printing or imaging characters.

Another object of the present invention is to provide a font managing apparatus for a character generator providing interchangeable font cartridges wherein an arbitrary font cartridge can be interchanged even if it is used for character imaging and can be set if it is not set yet without causing errors.

One more object of the present invention is to provide a font managing apparatus for a character generator having selectable fonts which is able to manage directories of various fonts efficiently without increasing a volume of a system RAM.

Further object of the present invention is to provide a font managing apparatus for a character generator having a variety of selectable fonts wherein a desirable font can be designated in the basis of a human sense thereto without indicating attributes thereof exactly.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects and features of the present invention will become more apparent when the preferred embodiment of the present invention is described in detail with reference of accompanied drawings in that;

FIG. 1 is a block diagram of a printer system to which the present invention is applied;

FIG. 2 is a block diagram showing a bit map data processor and a print engine of the printer system shown in FIG. 1;

FIG. 3 is a block diagram showing a bit map controller provided in the bit map data processor shown in FIG. 2;

FIG. 4 is a diagram showing the composition of a font cartridge;

FIGS. 5(a) and 5(b) show a structure of a code in a global data to be used for discriminating character type;

FIG. 6(a) shows a structure of each FCB (Font control bank) to be used for managing fonts;

FIG. 6(b) shows an alignment structure of FCBs;

FIG. 7 shows a composition of each FCB in detail;

FIG. 8(a) shows a composition of a ring buffer for storing data of D-BANKs;

FIG. 8(b) shows a state wherein several D-BANKs are registered;

FIGS. 9(a), 9(b) and 9(c) show a manner for registering a new D-BANK;

FIG. 10(a) shows a composition of a VFCB (Virtual font control bank);

FIG. 10(b) shows an alignment structure of VFCBs;

FIG. 11 shows a composition of each VFCB in

FIG. 12 is a diagram showing various methods for selecting a font;

FIG. 13(a) is a composition of data to be used for selecting a font;

FIG. 13(b) is a composition of a font attribute defined by plural parameters;

FIGS. 14(a) and 14(b) is a flow chart of the main routine to be executed by CPU of the bit map controller;

FIG. 14 is a partial flow chart showing a variation of the main routine;

FIG. 15 is a flow chart of a subroutine for reading font attributes;

FIG. 16(a) is a flow chart of a subroutine for font status initial setting;

FIG. 16(b) is a partial flow chart showing a variation of the subroutine shown in FIG. 16(b);

FIG. 17 is a flow chart of a subroutine for font information registration;

FIG. 18 is a flow chart of a subroutine for font directory registration;

FIG. 19 is a flow chart of a subroutine for initial font selection;

FIG. 20 is a flow chart of a subroutine for font selection by logic font code;

FIG. 21 is a flow chart of a subroutine for setting a font cell;

FIG. 22 is a flow chart of a subroutine for font renewal;

FIG. 23 is a flow chart of a subroutine for VFCB registration;

FIG. 24 is a flow chart of a subroutine for reading down font pattern data;

FIGS. 25(a) and 25(b) are flow charts of a subroutine for font selection by slot and F-BANK Nos.;

FIG. 26 is a flow chart of a subroutine for font selection by font name;

FIG. 27 is a flow chart of a subroutine for font ID registration;

FIG. 28 is a flow chart of a subroutine for font selection by ID No.; and

FIG. 29 is a flow chart of a subroutine for altering virtual font attributes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

(a) Composition of the electro-photographic printer

FIG. 1 shows a block diagram of an electro-photographic printer system to which the present invention is applied.

Data sent from an external data processor 1 such as a host computer are stored in a file buffer 2 once in order to improve through-put of the external data processor 1 and stored data are outputted from the file buffer 2 to a printing system 10.

The printing system 10 is comprised of a data processor 3 of bit map type, a print engine 4 with use of an electro-photographic processor and a laser means and optional apparatuses such as an external paper supplying unit 5 and a sorter 6.

FIG. 2 shows a schematic block diagram of the data processor 3 of bit map type.

The data processor 3 (hereinafter referred to BMU) is comprised of a bit map controller 30 (hereinafter referred to BMC), a RAM 32 for bit map (hereinafter referred to BM-RAM 32, a bit map writer 31 for imaging characters on BM-RAM 3 and font means 33. A font detecting sensor 339 is responsive to the font means 33 to detect the presence of a font cartridge. BMU 3 is connected to the print engine 4 by a bus B3 for control data and a bus B4 for image data.

The print engine 4 includes three controllers. The first one is an interface controller 40 (hereinafter referred to IFC) for executing processing of control data sent from BMC 30, control of an operation panel 44 and timing control for the print engine 4 through an internal bus B5. The second one is an electro-photographic controller 41 for controlling an electro-photographic processor 45 in accordance with data sent from IFC 40 through the internal bus B5. The third one is a print head controller 42 (hereinafter referred to PHC) controlling a semiconductor laser (not shown) and a polygon motor (not shown) of a print head 43 in accordance with information sent from IFC 40 through the internal bus B5 in order to write image data on a photoconductive drum provided in the electrophotographic processor 45 which is sent from BMW 31 through the internal bus B4. The external paper supply unit 5 and the sorter 6 are also controlled by IFC 40 through the internal bus B5.

The printer system 10 is so called laser printer of bit map type. Print data sent from the external data processor 1 are imaged as bit images on BM-RAM 32 of BMU 3 and bit images are outputted to the print engine 4. The print engine 4 drives the semiconductor laser to write those images as a latent image on the photoconductive drum and a toner image obtained by developing the latent image with toner is transferred onto a paper.

Data sent from the external data processor 1 includes codes for controlling the print format and setting modes of the print engine other than character codes.

BMU 3 analyzes protocols of these codes other than character codes and outputs commands for controlling the print format, passing a paper and altering modes of the optical apparatuses to the print engine 4.

The print engine 4 executes various control such as control of the electro-photographic system accompanied with the image control, timing control of a print paper and processing in synchronous with timing of feeding the print paper to the optional apparatus. The method for controlling the print engine 4 is substantially same to that of an electro-photographic copy machine except for control of the scanning system.

FIG. 3 shows a block diagram of BMC 30.

BMC 30 is comprised of some blocks interconnected by an internal bus B301. A CPU 301 (hereinafter referred to BM-CPU) forms a main part of BMC 30 which communicates with the external data processor 1 and/or the file buffer 2 through an interface 308 for the external data processor 1, transforms print data (code data) into bit images, controls BMW 31 through an interface 306 therefore and controls the print engine 4 through an interface 307 therefor. A system ROM (SYS-ROM) 302 memorizes programs for BM-CPU 301. A system RAM (SYS-RAM) 303 is an area for processing data and memorizing stacks and fundamental flags.

A register buffer (R-buffer) 304 is a buffer provided for communicating with the external apparatus such as the external data processor 1 and the file buffer 2 which enables to execute programs of BM-CPU 301 and communication with the external data processor 1 in asynchronous with each other.

A packet buffer (P-buffer) 305 memorizes data sent from the external data processor 1 as intermediate codes (hereinafter referred to packet codes) which are obtained by transforming data based on attributes of a selected font so as to make imaging bit images onto BM-RAM 32 easier.

The font means 33 provides memory area for interchangeable font cartridges (not shown) mounted. In each font cartridge, pattern data of fonts of eight kinds at the maximum can be stored, as will be explained later. The external data processor 1 selects a font among all fonts stored in respective font cartridges.

The font once selected can be changed to another one even in imaging characters and, also, it is not prohibited to interchange the font cartridge wherein the font used for imaging characters at the present is stored.

Although real imaging operation is done by BMW 31, it becomes necessary to calculate parameters such as internal addresses of pattern data in the selected font and writing addresses on BM-RAM 32. It takes a relatively long time. In order to speed up the processing, data of the next page is processed beforehand in printing bit images formed on BM-RAM 32 and processed data is stored in P-buffer 305. As P-buffer 305, it is desirable to use a first-in.multidot.first-out memory (FIFO).

A print engine interface 307 is an interface for the print engine 4 which communicates JOB information such as a number of prints and JOB control commands such as print command with an interface of the print engine 4 through the bus B3.

(b) Font management

(1) Composition of the font cartridge

FIG. 4 shows a composition of a font cartridge inserted in a slot. Each font cartridge is comprised of eight banks from F-BANK 0 to F-BANK 7 which is comprised of a ROM or RAM. Font pattern data of each font is stored in one or more banks. Since, for example, font pattern data of a font of Chinese characters (Kanji) has a large volume, two or more banks are assigned to memorize font pattern data. However, it is prohibited to store font pattern data belonging to two or more fonts of different kinds in one bank. Also, it is prohibited to store font pattern data belonging to one font extending over two or more slots.

As shown in FIG. 4, in the No. 1 slot, four kinds of fonts FONT 1, FONT 2, FONT 3 and FONT 4 are memorized in banks F-BANK 0, F-BANKs 1 and 2, F- BANK 3 and F-BANKs 4 to 6, respectively. The last bank F-BANK 7 is empty. To respective fonts FONT 1 to FONT 4, internal logic codes 0 to 3 and F-BANK NUMBERS 0, 1, 3 and 4 indicating respective numbers of top F-BANKs from which fonts start, respectively.

In the No. 2 slot, FONT 5 is stored extending over three F-BANKs from 0 to 2 and FONT 6 is stored extending over F-BANKs from 3 to 7.

Other slots have an essentially same composition as No. 1 or No. 2 slot.

These slot No. and F-BANK No. are used for selecting a font, as will be explained later.

As font memories for the font cartridge, both of font ROM and rewritable font RAM are usable. The font RAM is used as memory for loading font pattern data from an external machine such as a host computer down thereto. There may be two cases with respect to the font RAM that font pattern data has been down loaded and that font pattern data has been unloaded. There are two types about the font RAM. One of them is of a type which is backed up with a back up power source and has an externally operable input switch. In this type, font pattern data once loaded down is maintained.

Another type does not have any back up means and therefore, font pattern data is cancelled when the power is switched off.

As will be explained later, the top byte of the font RAM is used as discrimination information. The font RAM, into which font pattern data is considered to be written according to information regarding the external input switch or font managing information (FCB), is registered as a loaded RAM.

Each font data is comprised of font global data, directory and individual dot patterns.

In the font global data, a font name of ASCII 6 is included. The font name is used for selection of a font, as will be explained later.

FIG. 5(a) shows a structure of a code which is included in the global data for discriminating character type. The code is comprised of eight bits from b0 to b7 and upper three bits (b.sub.7, b.sub.6, b.sub.5) are used to indicate a wide classification and lower five bits (b.sub.4, b.sub.3, b.sub.2, b.sub.1 and b.sub.0) are used to indicate a narrow classification. The wide classification is the most important discrimination information for management of fonts and, as an example, shown in the next table.

TABLE ______________________________________ Wide Classification Narrow Classification ______________________________________ 0 Alphabetical typewriter 1 Alphabetical typewriter 2 -- 3 -- 4 JIS KANJI code 5 -- 6 for form overlay 7 for down load ______________________________________ *JIS (Japanese Industrial Standard)

FIG. 5(b) shows a structure of the narrow classification of a font of JIS KANJI code system as an example.

The narrow classification code is comprised of a character style code of upper three bits (b.sub.4, b.sub.3 and b.sub.2) and combination information code of lower two bits (b.sub.1 and b.sub.0) In FIG. 5(b), ANK indicates the alphabetical character and "Kana" character.

The structure of the narrow classification is defined in a proper manner to the wide classification to which the former belongs.

Font global data is read out when the power switch is switched on or when the font cartridge is interchanged and read out font global data is memorized as FCB (font control bank) in SYS-RAM 303 upon registration of font information.

(2) FONT MANAGEMENT INFORMATION (FCB)

BMC 30 executes fundamental management for fonts based on internal logic codes which are registration numbers given upon registration into FCB (Font Control Bank), as will be explained later.

FIG. 6(a) shows a composition of each FCB.

FCB is comprised of ECB status, FCB information, physical position information, cartridge information and logic font attribute. The logic font attribute is defined as attribute registered in the font management information of each available font. As shown schematically in FIG. 6(b), respective FCBs of all available fonts are memorized in SYS-RAM 303 in the order of internal logic font codes given upon registration of FCB.

FIG. 7 shows a composition of FCB in detail.

As mentioned in FIG. 6(a), FCB is comprised of FCB status, FCB information, physical position information, cartridge information and logic font attribute. All data of addresses from .phi. to 1FH are formed upon selection of a font. Slot number at 2nd address and bank number in slot at 18-th and 19-th addresses are used for selection of a font, respectively.

Data of addresses from 20 to 2F is font global data (cartridge information) read from respective cartridge.

FCB status is provided for indicating statuses of various flags.

Flags are defined as follows:

BUILD for indicating completion of FCB registration;

FONT for indicating font style;

ROM/RAM for indicating whether the memory of cartridge is ROM or RAM;

KANJI for indicating a chinese character font;

DOWN-LOAD for indicating a font cartridge for loading system programs and the like;

READY for indicating an enable state of font selection

LOADED for indicating whether font data is loaded into a font RAM or not;

FDIR for indicating registration of a font directory; and

SPECIAL for indicating a special font.

FCB information includes data as follows:

slot number, font address defined by linear address in a slot, top bank number of font directory registration, number of D-BANK indicating a number of banks into which respective font directories have been registered, starting address of "Kanji" font pattern indicating the top address of "Kanji" font pattern, font size indicating total number of bytes constituting font pattern data, maximum character code indicating the largest character code having a directory and total byte number indicating a total volume of respective font.

Physical position information includes bank off-set indicating an off-set value of a bank determined upon generating addresses for accessing respective font and F-BANK number for indicating a bank number in respective slot.

Cartridge information (font global information) includes data as follows:

font style indicating a kind of use of a font,

font type indicating a kind of character type of a font,

font name for selecting a font by the name thereof,

maximum character code in a font, font cell width indicating the maximum width of character,

font cell height indicating the maximum height of character,

position of base line,

font registration number indicating an article number,

font volume information No. 1 indicating combination information and bank size information, and

font volume information No. 2 indicating a bank size coefficient.

The area of logic font attribute is provided next to the cartridge information although it is not shown in FIG. 7. The logic font attribute includes use code, character type, character kind, character pitch, character height, character style and character weight.

(3) DIRECTORY REGISTRATION AREA (D-BANK)

Font directory is management information indicating individual characters memorized in the font ROM. However, if the font ROM is accessed every character, the through-put of data is lowered since processing parallel to imaging characters becomes impossible.

In order to avoid this problem, the directory of the selected font is loaded into SYS-RAM 303. Since this enables the parallel processing of imaging characters, processing time can be shortened.

Directory registration area is provided next to the FCB area. As shown in FIG. 8(a), this is formed by 8 banks from D-BANK .phi. to D-BANK 7 of a ring buffer composition (one bank has a volume of 2 K bytes). Namely, D-BANK is defined as a section of the directory registration area.

Upon each registration of a font, plural D-BANKs can be used according to a directory size, if necessary.

FIG. 8(b) shows a state of directory registration of four kinds of fonts (cross hatched areas show D-BANK used upon directory registration). With respect to each directory, top bank No. and directory size (bank No.) are defined and registered at 7-th and 8-th addresses, respectively. Further, directory registration flag FDIR indicating that at least one directory has been registered in a D-BANK and status valid flag indicating the validity of font management information included in each FCB are registered at zero-th address for FCB status. Also, D-BANK flag indicating existence of directory information is provided in each D-BANK.

FIGS. 9(a), 9(b) and 9(c) show actions of a BANK pointer upon renewal of font directory.

If the font F5 having a directory of volume of three D-BANKs is selected in the state shown in FIG. 9(a) and the directory thereof is not registered, three D-BANK flags of D-BANKs from No. .phi. to No. 2 are reset at zero, respectively, as shown in FIG. 9(b). Then, the directory of the font F5 is loaded from D-BANK No. 7, as shown in FIG. 9(c).

(4) FONT REGISTRATION AREA (VFCB)

When an user designates a font by an identification number, the information of the designated font is memorized in a font registration area (hereinafter referred to VFCB) of SYS-RAM 303.

In such a case that a font is designated by an ID number, if the font cartridge containing the designated font is drawn out after registration of the ID number, another font having attributes close to those of the designated font is selected as far as it exists and, therefore, logic font code in VFCB is renewed. Thus, VFCB may have logic font code not corresponding to that of the designated font and the selected font is considered to be a virtual font in this case. In this context, the ID number is called VFCB code or virtual font code sometimes.

FIG. 10(a) shows a composition of each virtual font registration (VFCB) area.

VFCB area is provided in SYS-RAM 303. Considering possibility of expansion of the system, an area of 32 bytes is given to each VFCB.

As shown schematically in FIG. 10(b), all of VFCBs of available fonts are memorized, respectively.

VFCB is comprised of VFCB status determined upon entry of an ID number, logic font code and virtual font attributes. VFCB status includes a flag indicating that the VFCB has been registered and is valid. Logic font code is a registration number for managing fonts in internal processing and indicates FCB area in which respective font information is registered. Virtual font attributes are defined as those of VFCB set by an user in accordance with protocols from the external data processor 1.

Data composition of virtual font attributes is shown in FIG. 11 in detail.

Virtual font attributes include a use code, character type, character kind, character pitch, character height, character style and character weight each of which corresponds to individual global data and have the same data composition as that of logic font attributes of FCB.

(c) Font selection

As will be later explained in detail, there are three stages for selecting a font in the image editing processing.

Namely, initial font selection upon switching on the power source, font selection by protocols from the external data processor 1 and font selection after interchange of a font cartridge are performed.

When the power source of the printer is turned on, any selection is not requested by the external data processor 1. However, the printer has default values for initialization including a default value for font selection, and according thereto, font selection processing is executed.

The font selection by protocols from the external data processing 1 is performed according to either one of four ways, as shown in FIG. 12.

(1) Slot and Bank selection

As already explained in connection with FIG. 4, a slot number and an F-BANK number are assigned to each of mounted font cartridges upon reading font attributes and are registered in the corresponding FCB.

Accordingly, it is possible to select a desirable font directly by designating a slot number and an F-BANK number in the slot.

(2) Font name selection

As already explained in connection with FIG. 7, the font name is included in the global information of each FCB. Therefore, it is also possible to select a desirable font indirectly by designating a font name.

(3) ID selection

An user can assign an ID number to respective font freely.

Therefore, it becomes possible to select a desirable font by designating an ID number through the external data processor 1.

When a font is selected or designated, internal logic codes of the selected font including logic font code, slot number, BANK number, font name ID number and so on are selected. If the cartridge corresponding to the selected font is not mounted, another font having attributes closest to those of the selected font is searched and selected.

Selection information is comprised of these selected values and LAST SELECT MODE code. This LAST SELECT MODE code indicates the selection mode which was executed just before interchange of font cartridge among "slot and BANK" selection mode 1, "font name" selection mode 2 and "ID" selection mode 3. And, the code corresponding to the selection mode is set at an area assigned to LAST SELECT MODE. Upon renewal of selection information in the font selection, LAST SELECT MODE and corresponding selection value are renewed.

(4) Image selection

Although methods for font selection above mentioned are dependent on physical information such as physical position of the slot, the image selection is dependent on images regarding each font.

This image selection includes first and second methods as follows.

According to the first method, individual nicknames are given to identify respective attributes of each VFCB. Nicknames are prepared for Style, Width, Height and Thickness (Weight). As nicknames for Style, "Normal" and "Italic" are prepared to indicate levels of Style. As nicknames for Width, numerals representing character pitches are prepared to indicate individual levels of the character size. As nicknames for Height, numerals representing points of character are prepared to indicate individual levels of the character height. As nicknames for Thickness, "Light", "Medium", "Bold" and "Extra bold" are prepared to indicate levels of the character weight.

TABLE 2 ______________________________________ Absolute level Nickname -2 -1 0 +1 +2 ______________________________________ Style Normal Normal Normal Italic Italic Width (Pitch) 20 15 12 10 6 Height 6 9 12 18 24 Thickness Light Light Medium Bold Extra (weight) Bold ______________________________________

When these nicknames are entered, an absolute level is searched and determined in accordance with the combination of entered nicknames and attributes of the corresponding VFCB are renewed into values of attributes of a font identified by the determined absolute level

As is clearly shown in Table 2, the character width and height become large and the character weight becomes thick as the absolute level increases.

Although all of default values in Table 2 are given beforehand, they can be set at user's side.

According to the second method, properties each of which is comprised of plural font attributes are represented by respective nicknames in order to identify an absolute level. These nicknames are chosen so as to fit to human senses. This enables to select or designate a font according to images or impressions thereabout.

Table 3 shows an example of nicknames.

TABLE 3 __________________________________________________________________________ Absolute level Nickname -2 -1 0 +1 +2 __________________________________________________________________________ Emphasis Weight Light Light Medium Bold Bold Pitch 15 12 12 12 10 Softness Type Normal Italic Normal Italic Normal Kind Gothic Gothic Courier Courier Times- roman Total Pitch 20 15 12 10 6 size Height 6 9 12 18 24 __________________________________________________________________________

The nickname "emphasis" is defined by the character weight and the character pitch so as to correspond to either one of absolute levels from (-2) to (+2). Similarly, the nickname "softness" is defined by the character type and the character kind and the nickname "total size" is defined by the character pitch and the character height.

When respective nicknames and relative levels of them are designated, an absolute level is searched and determined in accordance with these data and values of attributes corresponding to the determined absolute level are registered as a VFCB.

The processing for altering the font can be done similarly to that of the first method. However, the number of attributes corresponding to one nickname is different from that of the first method. It is difficult to search an absolute level in the second method since attributes of VFCB are defined as parameters. In order to avoid this problem, it is desirable to provide tables for memorizing respective absolute levels corresponding to nicknames, as shown in FIG. 13(b).

Each nickname can be defined by three or more attributes.

Font reselection to be done after interchange of the font cartridge, after down-load of font data or upon selection by various emulaters can be done as follows.

At first, font attributes are read into again, then LAST SELECT MODE data is read out and a font is selected in accordance with select values corresponding thereto. If this font selection is impossible to do, a font defined by default values is selected similarly to the case of switching on of the power source.

Font RAM is treated as follows.

If it is not backed up with a back-up power source, font data which have not been registered in an FCB is registered thereinto upon renewal since it is considered to be unloaded or mounted newly.

If it is backed up with a back-up power source, it is decided according to information of the external input switch whether font data has been registered in the FCB or not.

(d) Image Edition and Initialization

FIGS. 14(a) and 14(b) show the main routine to be executed by CPU 301 of BMC 30.

When the power switch is switched on, internal initialization is performed at step #1 and SYS-RAM 303 and BM-RAM 32 are cleared at step #2. Next, font attributes such as cell size are read into at step #3 and, then, initial settings such as initial setting by switches, initial setting of internal default values including default values for selecting a font and initial font selection are executed at step #4.

As initial settings by switches, resolution upon imaging, protocol transformation tables corresponding to various protocols and interface switching (CENTRONICS, RS 232C) are set. As initial settings by internal default values, initial font selection and initial margin setting are performed. Thereafter, the process enters into a processing loop for data received from the external data processor 1.

When at least one font cartridge is interchanged or when font data is down-loaded (at step #11 or #12), attributes of respective font are read similarly to the case of switching on the power switch since available fonts are changed (at step #15). At step #16, LAST SELECT MODE is read out and the font selection is done in accordance with select values corresponding to the LAST SELECT MODE at step #17. If it is decided impossible, a font in the BANK of the minimum number of the slot having the minimum number is selected as the default font at step #19.

These steps from #11 to #19 can be replaced with steps from #11' to #14' in FIG. 14'. Namely, a flag is read at step #11' which is set according to information given by means for detecting interchange of the font cartridge. If a font cartridge is now being interchanged, the process waits until the interchange of font cartridge is finished. However, data receiving operation is continued during the waiting time. If a font cartridge is not in interchanging, it is decided at step #12' whether or not font altering operation has been finished If the font having been selected is to be altered, attributes of each font is read into at step #13' and, then, a font is reselected at step #14'. Namely, renewal of internal information is executed according to the font alteration and the default font which is selected upon switching on the power source is reselected.

As stated above, the font reselection is requested upon the interchange of font cartridge or upon down-load of font from the external data processor 1. As to alteration methods of font and internal information, they will be explained later. According to this processing, analysis of received data is not performed in altering a font. This enables to avoid data error