+#
+/*
+ * px - Berkeley Pascal interpreter
+ *
+ * Version 2.0, January 1979
+ *
+ * Original version by Ken Thompson
+ *
+ * Substantial revisions by Bill Joy and Chuck Haley
+ * November-December 1976
+ *
+ * Rewritten for VAX 11/780 by Kirk McKusick
+ * Fall 1978
+ *
+ * Px is described in detail in the "PX 1.0 Implementation Notes"
+ * The source code for px is in several major pieces:
+ *
+ * int.c C main program which reads in interpreter code
+ * 00case.s Driver including main interpreter loop
+ * dd*.s Where dd are digits, interpreter instructions
+ * grouped by their positions in the interpreter table.
+ * p*.c Various C language routines supporting the system.
+ *
+ * In addition there are several headers defining mappings for error
+ * messages names into codes, and a definition of the interpreter transfer
+ * table. These are made by the script Emake in this directory and the scripts
+ * in the directory '../opcodes'.
+ */
+
+long argc;
+char **argv;
+
+/*
+ * Pascal runtime errors transfer to the routine
+ * 'error' in the file perror.c to decode them.
+ */
+int perrno; /* number of error which occurred */
+
+/*
+ * Definitions for memory allocation
+ * Memory allocation is done by palloc in utilities.c
+ */
+
+/*
+ * The file i/o routines maintain a notion of a "current file".
+ * The printing name of this file is kept in the variable
+ * "file" for use in error messages.
+ */
+char *file; /* ptr to active file name */
+long fchain; /* head of active file chain */
+int bufopt; /* controls flushing of std output as follows:
+ * 0 => flush on every write
+ * 1 => flush before std read or at end of line
+ * 2 => normal buffering
+ */
+/*
+ * THE RUNTIME DISPLAY
+ *
+ * The entries in the display point to the active static block marks.
+ * The first entry in the display is for the global variables,
+ * then the procedure or function at level one, etc.
+ * Each display entry points to a stack frame as shown:
+ *
+ * base of stack frame
+ * ---------------
+ * | |
+ * | block mark |
+ * | |
+ * --------------- <-- display entry points here
+ * | |
+ * | local |
+ * | variables |
+ * | |
+ * ---------------
+ * | |
+ * | expression |
+ * | temporary |
+ * | storage |
+ * | |
+ * - - - - - - - -
+ *
+ * The information in the block mark is thus at positive offsets from
+ * the display pointer entries while the local variables are at negative
+ * offsets. The block mark actually consists of two parts. The first
+ * part is created at CALL and the second at entry, i.e. BEGIN. Thus:
+ *
+ * -------------------------
+ * | |
+ * | Saved lino |
+ * | Saved lc |
+ * | Saved dp |
+ * | |
+ * -------------------------
+ * | |
+ * | Saved (dp) |
+ * | |
+ * | Current section name |
+ * | and entry line ptr |
+ * | |
+ * | Saved file name and |
+ * | file buffer ptr |
+ * | |
+ * | Empty tos value |
+ * | |
+ * -------------------------
+ */
+\f
+/*
+ * Structure for accessing things in the block mark
+ */
+struct stack {
+ long *tos; /* pointer to top of stack frame */
+ char *file; /* pointer to active file name */
+ long buf; /* pointer to active file record */
+ struct {
+ char name[8];/* name of active procedure */
+ short offset; /* offset of procedure in source file */
+ } *entry;
+ struct stack *disp; /* previous display value for this level */
+ struct stack **dp; /* pointer to active display entry */
+ long lc; /* previous location counter */
+ long lino; /* previous line number */
+ } *display[40];
+
+long addrsze; /* size of display addresses */
+
+
+/*
+ * Program option variables
+ */
+long stcnt; /* number of statements executed */
+long stlim; /* max number of statements to execute */
+long llimit; /* max number of lines per text file */
+short nodump; /* 1 => no post mortum dump */
+short mode; /* mode of input to interpreter */
+#define PX 0 /* normal run of px */
+#define PIX 1 /* load and go */
+#define PIPE 2 /* bootstrap via a pipe */
+\f
+/*
+ * Pxp variables
+ */
+char *pxpbuf; /* pointer to pxp buffer */
+long pxpsize; /* size of pxp buffer */
+
+#ifdef profile
+/*
+ * Px execution profile data
+ */
+#define numops 256
+struct cntrec {
+ double counts[numops]; /* instruction counts */
+ long runs; /* number of interpreter runs */
+ long startdate; /* date profile started */
+ long usrtime; /* total user time consumed */
+ long systime; /* total system time consumed */
+ double stmts; /* number of pascal statements executed */
+ } profdata;
+long profcnts[numops];
+#define proffile "/usr/ucb/pascal/px/pcnt.out"
+FILE *datafile; /* input datafiles */
+#else
+int profcnts; /* dummy just to keep the linker happy */
+#endif
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