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Operating Environments and Programming Languages...

Color BASIC

The authors first thought was to make separate sections

dealing with these two subjects. This wouldn’t really be

appropriate for the CoCo though. It’s main operating envi-

ronment, Color BASIC, is also a programming language!

Like many of the first generation of "home" computers, the

CoCo is ready to go as soon as it is turned on. All of these

computers (Timex/Sinclair ZX & TS series, Commodore

VIC-20, 16, & 64, Atari 400 & 800, Colleco Adam, TI 99/

4A, etc.... even the IBM PCjr) have a BASIC programming

language stored in a ROM chip. The ROM is active after

power is turned on, meaning that nothing has to be loaded

before beginning to operate the computer (unless working

with a pre-recorded program). This was done to make the

computers seem less intimidating. Cartridge slots were also

a part of most early home computers. A cartridge containing

a different ROM chip (Tandy ROM-Pak) could be inserted

before turning the system on, and when powered up whatever

was in the cartridge ROM would be ready to go. What could

be simpler?

There are four types of BASIC for the CoCo in three

versions: Color BASIC, Extended Color BASIC, Disk

BASIC and Super Extended Color BASIC. Color BASIC

is the simplest form of BASIC for the CoCo. It came in an 8K

ROM and was the first BASIC available. There were no

definition commands (DEFUSR, DEF FN, etc.), only one

trigonometric function (SINe), no error trapping, and few

graphics commands (only POINT, SET, and RESET). If a line

was typed in wrong, it would have to be retyped- there was no

editing capability. This BASIC was very similar to TRS-80

Model I Level I BASIC. CoCos with only this BASIC in-

stalled would display "COLOR BASIC VERSION 1.0" on

screen when turned on.

It didn’t take Tandy long to realize that programmers wanted

more. Extended Color BASIC (ECB, similar to TRS-80

Model I Level II) was announced when the CoCo was intro-

duced in September 1980, with an expected introduction of

"late November". It actually arrived in mid January, 1981.

Extended BASIC contained many new commands in another

8K ROM that plugged into a socket next to the existing

Color BASIC ROM, for a combined total of 16K. New

commands included those "missing" from Color BASIC,

including a wide range of graphics commands, algebraic and

trigonometric functions, the play command, and many new

programming statements- the most notable being a state-

ment to save machine language programs on tape. The

Extended ROM could be added to any CoCo for $99.00 plus

installation. Many of the graphics commands required 16K

to use (the first CoCo was only 4K), the upgrade would add

an additional $119.00 (plus installation) to the price. The

best deal was to purchase a 16K Extended CoCo new- it was

only $100 more than a 4K non-Extended model ($599 vs.

$499).

There were some minor problems in Color BASIC 1.0. One

was the printer driver. Tandy used a seven bit code to drive a

printer in the CoCo. Less than a year after the CoCo’s

introduction, printers (including Tandy models) standard-

ized on an eight bit code. Tandy first rectified this by

supplying a new printer eight bit printer driver on tape for

free (note that some early Tandy printers were seven bit

input, others were switchable between seven and eight bits).

This was brought on by the introduction of the Line Printer

VII, the first with a built-in CoCo serial connector (four pin)

and the first capable of dot addressable graphics. The seven

bit printer driver would print characters but no graphics.

In November 1981, the new 32K CoCo was introduced.

With it came a new revision of Color BASIC- version 1.1.

The main reason BASIC was changed was the 32K RAM

upgrade itself. The old 1.0 ROM would only address up to

16K, so it had to be changed. While the engineers were

making changes anyway, they decided to add some items to

the original ROM code and to fix a couple minor problems,

though the official stance was that nothing was wrong with

the 1.0 ROM. The additions included 32K support, the eight

bit printer driver, and displaying an "S" while searching a

cassette for a file and an "F" when a file was found.

When disk drives became available from Radio Shack in

October of 1981, a new BASIC extension came with them.

Rather than create a disk based operating system, Tandy

decided to add commands to BASIC that would allow access

to the disk drives. Disk Extended Color BASIC (DECB)

resided in an 8K ROM contained in the disk controller. With

the controller plugged in the disk commands loaded into the

Program-Pak area of Color BASIC. This method allowed the

CoCo to retain simplicity of use with the speed and conve-

nience of a disk drive. An advantage to BASIC programmers

is immediate access to disk information. A true disk loaded

disk operating system (DOS) not only has to have BASIC

loaded from disk, but BASIC has to call the DOS to access

most disk information. DECB has commands that allow

extensive disk data manipulation, including directly reading

and writing to specifiable portions of the disk.

A new type of CoCo 2, the Korean made "A" and "B" models

(and "A" or "B" follows the catalog number) required the last

revision of Color BASIC- version 1.3. These computers

used a different type RAM chip, the 4464, and required

different timing rates than previous DRAMs. A new SAM

(74LS285) also had to be used. The new SAM supported the

256 cycle RAM refresh rate required by the 4464 chips as

well as the 128 cycle refresh of the old style chips, so it

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