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% CPSC-LANGUAGE-OVERVIEW(7)
# NAME
cpsc-language-overview - supported cpsc pseudocode syntax
# DESCRIPTION
Keywords are uppercase and case-sensitive. Ordinary identifiers, including built-in function names, are case insensitive. Indentation is for readability; blocks use explicit closing keywords. Identifiers begin with a letter or underscore and continue with letters, digits, or underscores.
Assign with ASCII `<-`: `Count <- Count + 1`. Compare with `=`, `<>`, `<`, `>`, `<=`, and `>=`. Standard-library STRING comparisons compare contents, case-sensitively. Use `+`, `-`, `*`, and `/` for arithmetic; built-in `/` always returns REAL. Use `&` to join strings.
User-defined types can overload operators with OVERLOAD FUNCTION OPERATOR; expressions then use the declared result type. OVERLOAD definitions may also differ by return type: a context that requires a result type selects the matching return type, while a cast only prefers it. See [cpsc-keyword-operator(7)](keyword/cpsc-keyword-operator.7.md) and [cpsc-keyword-overload(7)](keyword/cpsc-keyword-overload.7.md). STRING cannot be implicitly converted to BOOLEAN. Typing is strict: arithmetic and unary minus accept only INTEGER and REAL, a comparison needs operands of the same type (or INTEGER with REAL), and BOOLEAN, CHAR and INTEGER never convert into one another implicitly (only INTEGER converts to REAL). Use ASC and CHR to move between CHAR and INTEGER. CHAR and STRING do convert implicitly: a CHAR becomes a one-character STRING in `&`, in comparisons, in assignment, in argument passing and in RETURN, and a STRING becomes a CHAR in assignment, argument passing and RETURN (for example `c <- MID(s, i, 1)`); a STRING whose length is not 1 is a runtime error that TRY/CATCH can catch. REAL never converts to INTEGER implicitly; use INT.
Precedence, from highest to lowest: unary operators, `* / DIV MOD`, `+ - &`, comparisons, AND, OR. Parentheses override precedence.
Parenthesized type casts, such as (C_INT)Number, have unary precedence. C_INT, C_CHAR, C_STRING and C_DOUBLE are native C aliases; TYPE name = C_TYPE("...") imports other supported C base types and pointers. Conversions between C and pseudocode types must be explicit. These are compiler extensions; see [cpsc-keyword-c_type(7)](keyword/cpsc-keyword-c_type.7.md). EXTERN "C" declares C functions from objects named with INCLUDE_OBJ; see [cpsc-keyword-extern(7)](keyword/cpsc-keyword-extern.7.md).
Literals include integers, decimal real numbers, TRUE/FALSE, strings in double quotes, and single-byte characters in single quotes. Negative numbers use unary minus. String and character literals support C++17 simple escapes (`\' \" \? \\ \a \b \f \n \r \t \v`), one to three octal digits, and `\x` followed by hexadecimal digits (byte values only). Unicode escapes `\uXXXX` and `\UXXXXXXXX` encode valid Unicode scalar values as UTF-8 in strings; in CHAR they must be ASCII. Unknown escapes are errors. Ordinary STRING literals retain NUL truncation, so `"a\0b"` is observed as `"a"`. An adjacent uppercase C suffix, as in `"text"C`, produces C_STRING directly. Comments begin with `//` and continue to the end of the line.
Declare variables before use. See DECLARE for built-in types and arrays, TYPE for records/enumerations/pointers, and CLASS for public/private fields and methods.
The compiler extensions TRY/CATCH/ENDTRY and THROW support anonymous exceptions with stack unwinding. Runtime check failures print the source line and error reason to standard error before throwing and can be caught. An uncaught exception also prints a generic termination message and returns status 1. There is no error object or what() support.
Multi-file builds use the compiler extensions INCLUDE and GLOBAL. Pass every source file on the command line and include the files whose definitions are needed. The entry file contains the sole top-level executable code, or a parameterless FUNCTION MAIN returning INTEGER; definitions alone do not form a runnable program.
PP_DEFINE and PP_UNDEF control file-local, case-sensitive preprocessor switches. PP_IFDEF and PP_IFNDEF conditionally include source up to PP_ENDIF; conditions may nest. Directives occupy their own lines, allowing leading whitespace and trailing // comments. Switches have no values and do not replace text. PP_DEFINE __LIB enables library runtime line reporting for subsequent source positions; PP_UNDEF __LIB restores ordinary behavior, including inside functions. See [cpsc-keyword-pp_define(7)](keyword/cpsc-keyword-pp_define.7.md) and [cpsc-keyword-pp_ifdef(7)](keyword/cpsc-keyword-pp_ifdef.7.md).
# KEYWORDS
- [cpsc-keyword-pp_define(7)](keyword/cpsc-keyword-pp_define.7.md): define or remove preprocessor switches and select library code regions.
- [cpsc-keyword-pp_ifdef(7)](keyword/cpsc-keyword-pp_ifdef.7.md): conditionally compile source according to switch definitions.
- [cpsc-keyword-include(7)](keyword/cpsc-keyword-include.7.md): import definitions from another compilation unit.
- [cpsc-keyword-global(7)](keyword/cpsc-keyword-global.7.md): declare shared primitive variables.
- [cpsc-keyword-constant(7)](keyword/cpsc-keyword-constant.7.md): declare a named literal with block scope.
- [cpsc-keyword-declare(7)](keyword/cpsc-keyword-declare.7.md): declare variables and arrays.
- [cpsc-keyword-input(7)](keyword/cpsc-keyword-input.7.md): read a value from standard input.
- [cpsc-keyword-output(7)](keyword/cpsc-keyword-output.7.md): print values to standard output.
- [cpsc-keyword-case(7)](keyword/cpsc-keyword-case.7.md): match values or ranges in order.
- [cpsc-keyword-if(7)](keyword/cpsc-keyword-if.7.md): choose between branches.
- [cpsc-keyword-try(7)](keyword/cpsc-keyword-try.7.md): catch or throw exceptions.
- [cpsc-keyword-while(7)](keyword/cpsc-keyword-while.7.md): repeat while a condition is true.
- [cpsc-keyword-repeat(7)](keyword/cpsc-keyword-repeat.7.md): repeat until a condition is true.
- [cpsc-keyword-for(7)](keyword/cpsc-keyword-for.7.md): iterate over an integer range.
- [cpsc-keyword-function(7)](keyword/cpsc-keyword-function.7.md): define a function that returns a value.
- [cpsc-keyword-procedure(7)](keyword/cpsc-keyword-procedure.7.md): define a procedure and parameter modes.
- [cpsc-keyword-operator(7)](keyword/cpsc-keyword-operator.7.md): overload unary and binary operators.
- [cpsc-keyword-overload(7)](keyword/cpsc-keyword-overload.7.md): explicitly overload functions, procedures and constructors.
- [cpsc-keyword-template(7)](keyword/cpsc-keyword-template.7.md): define function, procedure and class templates with type packs.
- [cpsc-keyword-call(7)](keyword/cpsc-keyword-call.7.md): invoke a procedure.
- [cpsc-keyword-openfile(7)](keyword/cpsc-keyword-openfile.7.md): open a text file.
- [cpsc-keyword-readfile(7)](keyword/cpsc-keyword-readfile.7.md): read a line from a text file.
- [cpsc-keyword-writefile(7)](keyword/cpsc-keyword-writefile.7.md): write a line to a text file.
- [cpsc-keyword-closefile(7)](keyword/cpsc-keyword-closefile.7.md): close a text file.
- [cpsc-keyword-type(7)](keyword/cpsc-keyword-type.7.md): define enumerations, pointers, and records.
- [cpsc-keyword-c_type(7)](keyword/cpsc-keyword-c_type.7.md): import native C types and explicitly cast values.
- [cpsc-keyword-extern(7)](keyword/cpsc-keyword-extern.7.md): declare and call C functions.
- [cpsc-keyword-include_obj(7)](keyword/cpsc-keyword-include_obj.7.md): link a C object file or the C library.
- [cpsc-keyword-delete(7)](keyword/cpsc-keyword-delete.7.md): destroy objects and release heap allocations.
- [cpsc-keyword-class(7)](keyword/cpsc-keyword-class.7.md): define a class with fields and methods.
- [cpsc-keyword-and(7)](keyword/cpsc-keyword-and.7.md): combine conditions with logical AND.
- [cpsc-keyword-or(7)](keyword/cpsc-keyword-or.7.md): combine conditions with logical OR.
- [cpsc-keyword-not(7)](keyword/cpsc-keyword-not.7.md): negate a condition.
- [cpsc-keyword-div(7)](keyword/cpsc-keyword-div.7.md): perform integer division.
- [cpsc-keyword-mod(7)](keyword/cpsc-keyword-mod.7.md): find the integer division remainder.
Closing and auxiliary keywords are documented with their main constructs: PP_UNDEF with PP_DEFINE; PP_IFNDEF/PP_ENDIF with PP_IFDEF; THEN/ELSE/ENDIF with IF; OF/OTHERWISE/ENDCASE with CASE; CATCH/ENDTRY/THROW with TRY; ENDWHILE with WHILE; UNTIL with REPEAT; TO/STEP/NEXT with FOR; RETURN/RETURNS/BYVAL/BYREF and function/procedure closing keywords with FUNCTION/PROCEDURE; READ/WRITE/APPEND with OPENFILE; ARRAY/OF and INTEGER/REAL/BOOLEAN/CHAR/STRING with DECLARE; ENDGLOBAL with GLOBAL; ENDTYPE with TYPE; EXTERN_FUNCTION/EXTERN_PROCEDURE with EXTERN; PUBLIC/PRIVATE/ENDCLASS with CLASS. TRUE/FALSE are BOOLEAN literals.
# STRING LIBRARY FUNCTIONS
These ordinary functions and the STRING class come from the embedded standard library, loaded and linked automatically unless **-no-std** is given. Ordinary string literals require a visible STRING class.
- [cpsc-function-length(7)](function/cpsc-function-length.7.md): find a string's length.
- [cpsc-function-mid(7)](function/cpsc-function-mid.7.md): extract part of a string.
- [cpsc-function-left(7)](function/cpsc-function-left.7.md): extract the beginning of a string.
- [cpsc-function-right(7)](function/cpsc-function-right.7.md): extract the end of a string.
- [cpsc-function-lcase(7)](function/cpsc-function-lcase.7.md): convert text to lower case.
- [cpsc-function-ucase(7)](function/cpsc-function-ucase.7.md): convert text to upper case.
- [cpsc-function-asc(7)](function/cpsc-function-asc.7.md): find a character's byte code.
- [cpsc-function-chr(7)](function/cpsc-function-chr.7.md): convert a byte code to text.
- [cpsc-function-is_num(7)](function/cpsc-function-is_num.7.md): test whether text represents a number.
- [cpsc-function-num_to_str(7)](function/cpsc-function-num_to_str.7.md): convert a number to text.
- [cpsc-function-str_to_num(7)](function/cpsc-function-str_to_num.7.md): convert text to a real number.
# MEMORY LIBRARY FUNCTIONS
These ordinary extension functions come from memory.cps, imported by std.cps automatically. Keyword NEW/DELETE use the same allocation runtime. With **-no-std**, import and supply memory.cps explicitly.
- [cpsc-function-malloc(7)](function/cpsc-function-malloc.7.md): allocate raw memory.
- [cpsc-function-realloc(7)](function/cpsc-function-realloc.7.md): resize an explicit allocation.
- [cpsc-function-free(7)](function/cpsc-function-free.7.md): release an explicit allocation.
# BUILT-IN FUNCTIONS
- [cpsc-function-eof(7)](function/cpsc-function-eof.7.md): test for the end of a text file.
- [cpsc-function-int(7)](function/cpsc-function-int.7.md): take the integer part of a number.
# UNSUPPORTED FEATURES
DATE, SET types and DEFINE, random-file operations (RANDOM/SEEK/GETRECORD/PUTRECORD), INT, RAND, whole-array assignment or return, array fields, and class inheritance (INHERITS/SUPER).
The individual pages note relevant differences from the Cambridge 2026 pseudocode guide. This manual describes the compiler's current support.
# EXAMPLE
```text
DECLARE Count : INTEGER
Count <- 2
IF Count > 0 THEN
OUTPUT "Count: " & NUM_TO_STR(Count)
ENDIF
```
# SEE ALSO
[cpsc(1)](../cpsc.1.md).
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