The User Interface

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The interface to work with this computer looks like below:

Here you can see.

  • The contents of the registers and
  • the state of the flags.
  • You can also see an input field, where you enter inputs when the program reaches an IN instruction.
  • There is an output field where the output of an OUT instruction will end up.
  • There is a message field, where messages like “Waiting for input” will show up.

There are also nine buttons.

  • RUN: Runs the program.
  • STEP: Take one step in the program.
  • CLR R: Clear the registers. I.e., sets them to 0. This includes the PC. It also resets the flags.
  • HLT: Stops the program if it is running.
  • RESET: Clears the registers, the flags, and the memory.
  • SLOWER: Make the program run half as fast.
  • FASTER: Make the program run twice as fast.
  • COPY: Copies the program to the clipboard.
  • PASTE: Restores a program from the clipboard.

Below all this, we have the memory and fields to enter and edit programs.

  • Address and contents field: Here we have the address of a cell, aa, and the contents of the cell, nn. We may, for example, have that cell number 17 has the contents 42. This will be written as 17 : 42 :
  • Edit field: Here, you enter the code and data used in a program.
  • Error message: Here, you will get error messages if you enter some erroneous data. Cells that have errors in them will be marked in red.
  • The cell that corresponds to the value the PC currently has (we say the cell that the PC points to) is marked with yellow.

Short codes

As the program is running,

  • “F” or “R”: Make the program run twice as fast.
  • “S”: Make the program run half as fast.
  • “H”: Halts the program.

When editing code.

  • Ctrl-S: Same as the STEP key.
  • Ctrl-R: Same as the Run key.
  • Ctrl-C: Same as the W key and the COPY button.
  • Ctrl-V: Same as the R key and the PASTE button.
  • Ctrl-I: Inserts a line at the position of the selected line.
  • Ctrl-D: Deletes the selected line.
Up a level : The ELIAC I
Previous page : The instruction set
Next page : ProgrammingLast modified: Jul 7, 2025 @ 14:22