Programming Languages and Paradigms The C Programming Language

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 2 Components of a C Program A C program is a collection of function definitions, (global) variable definitions, declarations and compiler directives Functions ( e.g., void push( char c ) { … } ) Variables ( e.g., int top; char Store[MAX]; ) Declarations ( e.g., void push( char c ); ) Compiler directives ( e.g., #define MAX 100 #include )

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 3 Built-in Data Types in C int, char, float Short and long versions of these data types short, long, double, long double, … No explicit boolean type in C Control structures that require conditions expect an int value 0 => false, non-zero => true

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 4 Composite Types Arrays Collection of elements of the same type Declaration: type varname[integer-value]; Structures Collection of elements of different types or with different names Declaration: struct strname { field declarations… }; struct strname varname; dot operator: varname.field

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 5 Pointers Address operator: & De-referencing operator: * Pointers and arrays Array names as addresses Pointer arithmetic Array access [] Dynamic allocation malloc, free, NULL Multi-dimensional arrays Pointers and structures: the -> operator

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 6 Strings String: sequence of characters (stored in a character array) The null (‘\0’) terminator String literals ( e.g., “hello” ) String functions ( ) strcpy strlen strcmp strcat …

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 7 Statements expression-statement Expression followed by a semicolon expr; where expr consists of variables, constants, operators, parentheses, function calls Block or compound-statement 0 or more statements enclosed in { } Declarations may precede statements { decl decl decl … stmt stmt stmt }

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 8 Statements (decision) if-statement Condition bounded by parentheses Numeric expression expected in condition Optional else clause switch-statement Can be viewed as a special kind of block Has entry points (through the case labels) and exit points (through break; statements ) switch expression should be of ordinal type

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 9 Statements (loops) while-statement Loop test at the beginning of the loop Loop body may not be executed at all do-while-statement Loop test at the end of the loop Loop body executed at least once for-statement for( expr1; expr2; expr3 ) stmt Has an equivalent while-loop formulation Used if there is an explicit loop control variable

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 10 Statements (others) break; Breaks out of the nearest enclosing loop or switch continue; Proceeds to the loop test return-statement return expr; Provides value return by a function Without expr (if return type is void), the statement simply causes control to be returned to the caller

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 11 Functions Function definition: Return type Name Parameters Body (block)

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 12 Parameter Passing In C, all parameters are pass by value Pointers and the address operator enable a function to update data outside of the function But the parameter passed (the address) is still a value

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 13 Module Organization in C Suppose mod.c is a module containing functions to be used by other C source files A mod.h file contains function prototypes and #define directives An #include directive is placed in the file using the module (i.e., #include “mod.h”). (Do you need to include it in mod.c?) Modules can be separately compiled and then linked with other modules to produce an executable

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 14 Scope Names in a { … } block are limited to that block Local variables Formal parameters of a function are local to the function body/block Declarations outside the functions are accessible from other functions extern declaration: compiler permits use of variables before they are defined static definition: variable use restricted to functions within file

6/15/2005 Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved. L2: C Slide 15 Library Functions The C standard library I/O, math, string functions and others Prototypes are in: …