Appendix G

The following table is a glossary of terms found in this manual:

BAUD - The term baud rate means the number of bits sent down a line per second. A baud rate of 300 will, therefore, be capable of transmitting data at 300 bits per second. Since a textual character is composed of 8 bits, then 37.5 characters could be sent per second at this baud rate.

BIOS - This means the Basic Input Output System. The BIOS is a fundamental portion of an Operating System, allowing the operating system to communicate correctly with any peripheral devices; typical BIOS modules include the disc driver; the keyboard input driver; the screen driver; the printer driver.

BIT - A bit is a binary digit. The bit can, therefore, contain either One or Zero. A One is bit HIGH or ON. A zero is bit LOW or OFF. A bit may be likened to a light-switch - the switch can only be on or off. See BYTE.

BOOT - This term comes from the phrase "the computer pulls itself up by its boot-strap". The term boot-strap means the same, but is no longer in such common use. To boot a computeris to load an operating system - the computer does this by means of a boot-strap program. The computer, when switched on, is not aware of its environment - but it automatically runs its boot-strap program. The Sirius 1 boot-strap program is stored in the boot PROM; it first causes the display of the little disc picture - it then searches for a disc with an operating system - when it finds this disc, it loads the operating system and begins to execute it. The boot-strap program is not used again until the reset switch is pressed, or the power is switched off and on.

BUS - A bus in computer jargon is not unlike a bus to carry passengers. When data is moved around inside a computer it is moved along the bus wires. These bus wires connect the Sirius 1 microprocessor to its memory, disc(s) and screen.

BYTE - A byte is a collection of 8-bits or two nibbles. A byte may store one character of text, or a number from 0 to 255 in binary.

DOT MATRIX - A printed character on the screen or a dot-matrix printer may be viewed as a square containing dots. On the Sirius 1 screen a character has a square cell (matrix) of 16 dots high by 10 dots wide - within this box, the dot on/off patterns create a viewable character.

FONT CELL - In reference to DOT MATRIX, the font cell is the collection of bytes of data that make up the character dots that are to be displayed on the screen. Each character on the screen is composed of pre-defined patterns of dots to make the viewed dot matrix. These patterns of dots are stored in the Sirius 1 memory as data - the screen controller chip scans these data bytes and the resulting character image is displayed on the screen.

HEADER - A header on a file gives information to the operating system on where and how the file is to be loaded in to memory. Many files that were provided by Victor Technologies (such as keyboard and character set files) contain headers that are not used by the operating system, but are used by Victor Technologies utilities.

INTERRUPT - An interrupt is some event occurring in the computer's environment that the computer will stop all other activities for. An example of an interrupt is a key-press. If you press a key on the Sirius 1, an interrupt is generated; at this point the processor stores all information on its current task and gets and saves the value of the key pressed; it then picks up all the information it stored on its last task and continues where it left off. This whole series of events takes only a few micro-seconds.

NIBBLE - Sometimes spelled NYBBLE; a nibble is half a byte or 4-bits. See BYTE and BIT.

OPERATING SYSTEM - An operating system allows the computer to be aware of its environment and gives the user the ability to enter and retrieve data from the computer.

PROM - Programmable Read Only Memory, PROM, is a chip or collection of chips that is used to store permanently a single computer program or collection of computer programs. The boot-prom, sometimes called boot-rom, contains all the information the Sirius 1 computer needs to read an operating system from disc. There are different types of prom; EPROM which is erasable prom, simply shine a high-powered ultra-violet lamp on the chip, and it can be re-programmed; etc.

RAM - Random Access Memory, RAM, is a chip or collection of chips that is used to store temporarily (until the power is removed) data, computer program(s), text, etc. This is the memory of a computer.

REGISTER - A computer register is a portion of the processor. The Sirius 1 uses the Intel 8088 micro-processor - there are several different types of registers within this chip; there are 8-bit registers, and 16-bit registers. Data is generally not manipulated in RAM, but is brought in to a register of the processor and manipulated there, then the result saved from the register back into RAM.

WORD - A word is a number of bits, generally greater than 8. The Sirius 1 has a 16-bit word - thus a word in the Sirius 1 is composed of two bytes. The DEC PDP-8 computer has a 12-bit word - on this machine, therefore, a word is composed of one byte and one nibble.