projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 82e84c76 BJ |
1 | /* |
| 2 | * px - UNIX Pascal interpreter | |
| 3 | * | |
| 4 | * Version 1.0, July 1977 | |
| 5 | * | |
| 6 | * Written by Bill Joy and Chuck Haley | |
| 7 | * November-December 1976 | |
| 8 | * | |
| 9 | * Based on an earlier version by Ken Thompson | |
| 10 | * | |
| 11 | * Px is described in detail in the "PX 1.0 Implementation Notes" | |
| 12 | * The source code for px is in several major pieces: | |
| 13 | * | |
| 14 | * int.c C main program which reads in interpreter code | |
| 15 | * 00int.s Driver including main interpreter loop | |
| 16 | * dd*.s Where dd are digits, interpreter instructions | |
| 17 | * grouped by their positions in the interpreter table. | |
| 18 | * p*.c Various C language routines supporting the system. | |
| 19 | * | |
| 20 | * In addition there are several headers defining mappings for error | |
| 21 | * messages names into codes, and a definition of the interpreter transfer | |
| 22 | * table. These are made by the script Emake in this directory and the scripts | |
| 23 | * in the directory '../opcodes'. | |
| 24 | */ | |
| 25 | ||
| 26 | int argc; | |
| 27 | char **argv; | |
| 28 | ||
| 29 | /* | |
| 30 | * Pascal runtime errors cause emulator traps | |
| 31 | * to the routine onemt which transfers to the | |
| 32 | * routine 'error' in the file perror.c to decode them. | |
| 33 | * This method saves at least one word per static error. | |
| 34 | */ | |
| 35 | int onemt(); | |
| 36 | ||
| 37 | /* | |
| 38 | * Definitions for memory allocation | |
| 39 | * Memory allocation routines are in 'palloc.c' | |
| 40 | */ | |
| 41 | char *bottmem, *memptr, *high, *maxstk; | |
| 42 | ||
| 43 | /* | |
| 44 | * The file i/o routines maintain a notion of a "current file". | |
| 45 | * The printing name of this file is kept in the variable | |
| 46 | * "file" for use in error messages. | |
| 47 | */ | |
| 48 | char *file; | |
| 49 | \f | |
| 50 | /* | |
| 51 | * THE RUNTIME DISPLAY | |
| 52 | * | |
| 53 | * The entries in the display point to the active static block marks. | |
| 54 | * The first entry in the display is for the global variables, | |
| 55 | * then the procedure or function at level one, etc. | |
| 56 | * Each display entry points to a stack frame as shown: | |
| 57 | * | |
| 58 | * base of stack frame | |
| 59 | * --------------- | |
| 60 | * | | | |
| 61 | * | block mark | | |
| 62 | * | | | |
| 63 | * --------------- <-- display entry points here | |
| 64 | * | | | |
| 65 | * | local | | |
| 66 | * | variables | | |
| 67 | * | | | |
| 68 | * --------------- | |
| 69 | * | | | |
| 70 | * | expression | | |
| 71 | * | temporary | | |
| 72 | * | storage | | |
| 73 | * | | | |
| 74 | * - - - - - - - - | |
| 75 | * | |
| 76 | * The information in the block mark is thus at positive offsets from | |
| 77 | * the display pointer entries while the local variables are at negative | |
| 78 | * offsets. The block mark actually consists of two parts. The first | |
| 79 | * part is created at CALL and the second at entry, i.e. BEGIN. Thus: | |
| 80 | * | |
| 81 | * ------------------------- | |
| 82 | * | | | |
| 83 | * | Saved lino | | |
| 84 | * | Saved lc | | |
| 85 | * | Saved dp | | |
| 86 | * | | | |
| 87 | * ------------------------- | |
| 88 | * | | | |
| 89 | * | Saved (dp) | | |
| 90 | * | | | |
| 91 | * | Current section name | | |
| 92 | * | and entry line ptr | | |
| 93 | * | | | |
| 94 | * | Saved file name and | | |
| 95 | * | file buffer ptr | | |
| 96 | * | | | |
| 97 | * | Empty tos value | | |
| 98 | * | | | |
| 99 | * ------------------------- | |
| 100 | */ | |
| 101 | int display[20], *dp; | |
| 102 | \f | |
| 103 | int lino; | |
| 104 | int nodump; | |
| 105 | ||
| 106 | /* | |
| 107 | * Random number generator constants | |
| 108 | */ | |
| 109 | long seed; | |
| 110 | double randa; | |
| 111 | double randc; | |
| 112 | double randm; | |
| 113 | double randim; | |
| 114 | ||
| 115 | /* | |
| 116 | * Structures to access things on the stack | |
| 117 | */ | |
| 118 | struct { | |
| 119 | char pchar; | |
| 120 | }; | |
| 121 | struct { | |
| 122 | int pint; | |
| 123 | int p2int; | |
| 124 | }; | |
| 125 | struct { | |
| 126 | long plong; | |
| 127 | }; | |
| 128 | struct { | |
| 129 | double pdouble; | |
| 130 | }; | |
| 131 | ||
| 132 | char discard; |