DIAL-MS File Commands Program Description

This document describes FILECOMS, a set of file handling routines integrated within the LAP6-DIAL editor, filing system, and assembler for the PDP-12 computer. Developed in 1970 by Software Services, FILECOMS is derived from Mary Allen Wilkes's LAP6 program and PDP-8 computer programs like PAL-D.

FILECOMS is invoked by the Editor for critical operations such as printing source code, adding binary files, saving programs, saving binary files, and assembling source files. It is responsible for validating requests, setting up necessary arguments, and managing file storage and retrieval. If a command cannot be executed, FILECOMS displays a "NO" message.

A central component of FILECOMS is its index structure, located on tape blocks 346 and 347. This two-block index, identified by a specific DIAL code, stores information for up to 77 octal file names. Each file entry in the index occupies 10 words, with the first four reserved for the file name (up to eight characters). Words 5 and 6 store the starting tape block (TBLK) and length of a source file, while words 7 and 8 do the same for a binary file. Special values (5757) indicate the absence of source or binary data.

Key operations handled by FILECOMS include:

• Save Program: Locates space in the file area (divided into upper and lower sections), manages the index (checking for existing names and allowing replacements), and transfers program blocks from the working area to tape.
• Print Source: Configures arguments for printing, either from the working area or a named file, checking the index for validity and source availability.
• Assembler: Sets up arguments for the Assembler when a source file is requested for assembly, utilizing index routines to locate the file.
• Save Binary: Reads the binary header, configures starting mode and address for PDP-8 or LINC mode, validates the starting address, determines the number of blocks, finds available space in the file area, and copies the binary data.
• Add Binary: Reads the index to locate the specified binary file, scans the file header for relocation information, processes binary data by moving non-zero words, and manages block counts and buffer refills.

The document also includes flow diagrams (attached), a program listing (attached), a memory map illustrating memory allocation for FILECOMS and other system components, and a symbol table.