Keeping Your Work

Introduction

Everything you type into Turbo's editor lives in the machine's memory until you save it, and memory forgets the moment the Einstein is switched off. The disc does not. This section is about the traffic between the two - and about the other thing Turbo can put on a disc, which is a finished program that runs on its own.

Saving

You met S in S4:

Saving A:HELLO.PAS

Do it often. It takes a second, and it is the difference between losing a minute's work and losing an evening's.

The first time you save a new program, the disc gains one file. Every time after that, it keeps two. Save HELLO a second time and then look with D:

HELLO    BAK : HELLO    PAS

HELLO.PAS is what you just saved. HELLO.BAK is the version it replaced - Turbo renames the old file rather than destroying it, so that if you have just saved something you regret, the one before is still there.

Files cost disc space, and not by the byte. The four-line HELLO program is well under a hundred bytes, but each file takes at least 2k of the disc: saving it, and then saving it again, takes Bytes Remaining from 80k to 76k. With 80k to start with, there is room for plenty of work, but .BAK files add up. The end of this section shows how to clear them away.

Loading

W with the name of a program that is on the disc loads it:

Loading A:HELLO.PAS

and no New File - that is how you can tell it found it. E then shows it in the editor, just as you left it.

If you have changed the program you are working on and not saved it, W stops to ask first:

Workfile A:HELLO.PAS not saved. Save (Y/N)?

Y saves it and then asks for the new name; N throws your changes away. Q asks the same question, for the same reason. Read it every time.

Tidying Up

Turbo can list the disc but not delete from it. The disc operating system can. Quit Turbo with Q, and at the 0: prompt type ERA, a space, and the file's full name:

0:ERA HELLO.BAK
0: HELLO   .BAK?

It asks before it acts. Press Y:

0: HELLO   .BAK?Y       Erased

Any other key leaves the file alone. If there is no such file it says No File. Type TURBO to go back.

ERA does not care whether it is erasing a .BAK or the only copy of a week's work. Give it the name you mean.

A Program That Runs On Its Own

When you press R, Turbo compiles your program into memory and runs it there, and the machine code vanishes when you leave Turbo. Turbo can also write the machine code to the disc, as a program the disc operating system can run by itself - the same kind of file as TURBO.COM.

Press O, for compiler Options:

compile -> Memory
           Com-file
           cHn-file

Find run-time error  Quit

The arrow says where compiled programs go. Press C and it moves to Com-file, and two lines about addresses appear, which you can ignore. Press Q to go back to the main menu, and press C, for Compile:

Compiling  --> A:HELLO.COM
  4 lines

Code:    57 bytes (1FC9-2002)
Free: 51379 bytes (2003-E8B6)
Data:   131 bytes (E8B7-E93A)

The arrow on the first line says where it went: a new file on the disc, HELLO.COM. Quit Turbo, and at the 0: prompt just type its name:

0:HELLO
Hello, Einstein
0:

No Turbo, no menu - your program, run as the machine runs any other.

It is bigger than you might expect. HELLO.COM is 8,064 bytes, for 57 bytes of your own code. Borland's manual explains why: a .COM file carries with it the part of Turbo that every Pascal program needs in order to run - Turbo's "run-time library" - because Turbo will not be there to provide it. On the disc, HELLO.COM and VERSE.COM each cost 8k.

Two things to know about Com-file mode:

• It lasts until you leave Turbo. The next time you start TURBO, the Options menu says Memory again. To go back sooner, O, M, Q.
• While it is on, R runs the .COM file rather than compiling into memory, and Turbo then has to load its own messages and your work file again from the disc. For the everyday edit-and-run of writing a program, stay in Memory.

Only On An MFI

MAME writes to the course disc because it is an .mfi. If you ever run Turbo from a .dsk image, the first save goes like this:

Saving A:HELLO.PAS
Bad Data 0:
Try Again(Y/N)?

Do not answer N. It does not return you to Turbo: it drops you straight out to the 0: prompt, and whatever you had typed is gone. There is no good answer from here; the lesson is to use the course disc.

The Code

This section's program is S4's exercise 4.2, the verse:

program Verse;
begin
  Writeln('Roses are red,');
  Writeln('Violets are blue,');
  Writeln('Turbo is quick');
  Writeln('And so are you.');
end.

Load it with W VERSE (or type it, and save it as VERSE), then O, C, Q, and C to compile it to VERSE.COM. Then Q, and at 0:, type VERSE.

Starting from

Turbo freshly started, Y; VERSE.PAS saved on the disc.

What you should see

After C: Compiling --> A:VERSE.COM, 7 lines, and Code: 141 bytes. At 0::

0:VERSE
Roses are red,
Violets are blue,
Turbo is quick
And so are you.
0:

Change One Thing

• Save the same program twice and look with D. What has appeared?
• Look at Bytes Remaining before and after you compile VERSE.COM. How much of the disc did it take?
• Start Turbo again after compiling to a .COM, and look at the Options menu. Where does the arrow point now?

Exercises

6.1 Make HELLO.COM from your S4 program, and run it from the 0: prompt.

6.2 Save your verse program as VERSE, restart the Einstein, and get it back into the editor.

6.3 Erase every .BAK file you have made, one at a time, and check with DIR that the programs themselves are still there.

Worked solutions are in Appendix II.

When It Goes Wrong

Summary

S saves, and the previous version becomes .BAK. W loads, and warns you first if your changes are not saved; so does Q. ERA at the 0: prompt erases a file, after asking. O, C, Q, C compiles your program into a .COM file that runs on its own from 0: - about 8k however small the program.

Next

S7, Sums - numbers, and making Turbo do arithmetic.