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InOut

The primary text I/O module for PIM4 programs. This is the module you will use most often for printing output and reading user input. It reads from stdin and writes to stdout by default, with optional file redirection.

Available in PIM4 mode (the default). No special flags needed.

Variables

Variable Type Description
Done BOOLEAN Set after every read operation. TRUE if the read succeeded, FALSE if input was invalid or unavailable (e.g., EOF). Write operations do not affect Done.

Procedures

Output

PROCEDURE WriteString(s: ARRAY OF CHAR);

Write a NUL-terminated string to stdout. This is the most common way to print text. The string is written up to the first NUL character (0C) or the end of the array, whichever comes first.

PROCEDURE WriteLn;

Write a newline character. Call this after WriteString or WriteInt to end the line -- output is not automatically newline-terminated.

PROCEDURE Write(ch: CHAR);
PROCEDURE WriteChar(ch: CHAR);

Write a single character to stdout. WriteChar is an alias for Write -- they do the same thing.

PROCEDURE WriteInt(n: INTEGER; w: CARDINAL);

Write a signed integer right-justified in a field of width w. If the printed number has fewer digits than w, spaces are added on the left. If it has more digits, it is printed in full (not truncated). Use w=1 for minimum-width output with no padding.

Example: WriteInt(-42, 6) prints " -42" (4 characters, padded to width 6).

PROCEDURE WriteCard(n: CARDINAL; w: CARDINAL);

Write an unsigned cardinal, right-justified in width w. Same padding rules as WriteInt.

PROCEDURE WriteHex(n: CARDINAL; w: CARDINAL);

Write n as a hexadecimal number (uppercase A-F), right-justified in width w. No 0x prefix is printed.

PROCEDURE WriteOct(n: CARDINAL; w: CARDINAL);

Write n as an octal number, right-justified in width w.

Input

PROCEDURE Read(VAR ch: CHAR);
PROCEDURE ReadChar(VAR ch: CHAR);

Read a single character from stdin. Sets Done to TRUE on success, FALSE on EOF or error. ReadChar is an alias for Read.

PROCEDURE ReadString(VAR s: ARRAY OF CHAR);

Read a whitespace-delimited token (word) from stdin into s. Leading whitespace is skipped. Reading stops at the next whitespace character or EOF. The result is NUL-terminated. Sets Done.

PROCEDURE ReadInt(VAR n: INTEGER);

Read a signed integer from stdin. Skips leading whitespace, reads optional sign and digits. Sets Done to FALSE if the input is not a valid integer.

PROCEDURE ReadCard(VAR n: CARDINAL);

Read an unsigned cardinal from stdin. Sets Done to FALSE if the input is not a valid number.

File Redirection

These procedures redirect subsequent reads or writes to a file instead of stdin/stdout. This is useful for simple batch processing. For more control over file I/O, use BinaryIO or FileSystem instead.

PROCEDURE OpenInput(ext: ARRAY OF CHAR);

Open a file for reading. After this call, Read, ReadString, ReadInt, and ReadCard read from the file instead of stdin. ext is the filename (not a file extension, despite the parameter name -- this is a PIM4 historical convention).

PROCEDURE OpenOutput(ext: ARRAY OF CHAR);

Open a file for writing. Subsequent Write, WriteString, WriteInt, etc. go to the file.

PROCEDURE CloseInput;
PROCEDURE CloseOutput;

Close the redirected file and restore stdin/stdout for subsequent I/O.

Example

MODULE InOutDemo;
FROM InOut IMPORT WriteString, WriteInt, WriteHex, WriteLn;
BEGIN
  WriteString("Decimal: ");
  WriteInt(255, 1); WriteLn;

  WriteString("Hex:     ");
  WriteHex(255, 1); WriteLn;

  WriteString("Padded:  [");
  WriteInt(42, 8);
  WriteString("]"); WriteLn
END InOutDemo.

Output:

Decimal: 255
Hex:     FF
Padded:  [      42]