Using the Tape Drive on the Simulator

Inserting/Removing a Cassette

The "Release" button (eject cassette on the Wang 700) will pop-up a file select dialog and allow you to select a file to use as a "tape cassette". An existing file may be used, although note that proper positioning is required unless you intend to overwrite the contents. If a new file name is typed in the dialog, then that file is created, empty. Clicking Release followed by Cancel (in the dialog window) will make the tape drive "empty", as if it had no cassette. Attempting to press "Ready" will fail, and attempts to load or record to the tape will hang with a blank display.

Positioning the Tape

The "Forward" and "Rewind" buttons will position the tape forward, or backward, by "records". Each "record" on the tape is marked with a special code to indicate internally that the recorded image ends. Note how this differs from the Wang 700 tape unit, where precise positioning using Forward and Reverse was difficult at best, if not impossible, due to the guesswork of where the tape records ended.

Note, there was a trick that can be used to manage the tape position. If the P.C. is set near the end of the range, and a program loaded, only the last 16 program steps will be overwritten. As long as no data or program steps in that range need to be preserved, multiple programs on one tape can be skipped.

Simulator Details Note: The tape "record marks" in the file are two bytes, the first being 0x5c (END PROG) and the second being either 0x5c (if it represents a real END PROG) or 0xff in case the tape was simply stopped without recording an END PROG code. The rest of the bytes in the file directly correspond to data, either program steps or digit-pairs from registers.

Making the Tape Ready for Operations

In order to record to, and load from, a tape the "Tape Ready" button must be depressed. This is the only button on the tape unit that toggles. All others are "momentary operation". Pressing any of the buttons on the tape when Ready is engaged will release the Ready button, making the tape unit "not ready". This is especially noticeable when using the tape positioning buttons.

Loading a Program

When the tape positioned as desired (typically at "record 0") and the "Tape Ready" button depressed, click the LOAD PROG button. The display will blank momentarily (depending on the length of the program) and then come back on. The tape position indicator should have advanced.

Verifying a Loaded Program

Pressing the VERIFY PROG button will execute a "check sum" of all program codes (except the END PROG) and display that sum. This number can be compared to a known result to confirm that the program is properly loaded and is ready to run.