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Department of Information Technology

Department of Information Technology. Computer Programming & Problem Solving Ch 3 Functions. Outline. Introduction Program Modules in C Math Library Functions Functions Function Definitions Function Prototypes . Objectives. In this chapter, you will learn:

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Department of Information Technology

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  1. Department of Information Technology Computer Programming & Problem Solving Ch 3 Functions KIC/Computer Programming & Problem Solving

  2. Outline • Introduction • Program Modules in C • Math Library Functions • Functions • Function Definitions • Function Prototypes KIC/Computer Programming & Problem Solving

  3. Objectives • In this chapter, you will learn: • To understand how to construct programs modularly from small pieces called functions.. • To introduce the common math functions available in the C standard library. • To be able to create new functions. • To understand the mechanisms used to pass information between functions. KIC/Computer Programming & Problem Solving

  4. Main program Function 1 Function 2 Function 3 Function 5 Function 4 Introduction Divide and Conquer • Construct a program from smaller pieces or components • These smaller pieces are called modules • Each piece more manageable than the original program KIC/Computer Programming & Problem Solving

  5. Program Modules in Ca • Functions • Modules in C • Programs combine user-defined functions with library functions • C standard library has a wide variety of functions • Function calls • Invoking functions • Provide function name and arguments (data) • Function performs operations or manipulations • Function returns results • Function call analogy: • Boss asks worker to complete task • Worker gets information, does task, returns result • Information hiding: boss does not know details KIC/Computer Programming & Problem Solving

  6. Program Modules in C Fig. 5.1 Hierarchical boss function/worker function relationship. KIC/Computer Programming & Problem Solving

  7. Math Library Functions • Math library functions • perform common mathematical calculations • #include <math.h> • Format for calling functions • FunctionName( argument ); • If multiple arguments, use comma-separated list • printf( "%.2f", sqrt( 900.0 ) ); • Calls function sqrt, which returns the square root of its argument • All math functions return data type double • Arguments may be constants, variables, or expressions KIC/Computer Programming & Problem Solving

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  9. Functions • Functions • Modularize a program • All variables defined inside functions are local variables • Known only in function defined • Parameters • Communicate information between functions • Local variables • Benefits of functions • Divide and conquer • Manageable program development • Software reusability • Use existing functions as building blocks for new programs • Abstraction - hide internal details (library functions) • Avoid code repetition KIC/Computer Programming & Problem Solving

  10. Function Definitions Function definition format return-value-type function-name( parameter-list ){ declarations and statements} • Function-name: any valid identifier • Return-value-type: data type of the result (default int) • void– indicates that the function returns nothing • Parameter-list: comma separated list, declares parameters • A type must be listed explicitly for each parameter unless, the parameter is of type int KIC/Computer Programming & Problem Solving

  11. Function Definitions Data typeFunction_name (Passing_Data); • Definitions and statements: function body (block) • Variables can be defined inside blocks (can be nested) • Functions can not be defined inside other functions • Returning control • If nothing returned • return; • or, until reaches right brace • If something returned • returnexpression; KIC/Computer Programming & Problem Solving

  12. Function Definitions Return_Data_TypeFunction_Name(Passing_Data) { Statment 1; Statment 2; Statment 3; return Val; } void print() { printf(“Build_Functions”); }

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  17. Function Prototypes • Function prototype • Function name • Parameters – what the function takes in • Return type – data type function returns (default int) • Used to validate functions • Prototype only needed if function definition comes after use in program • The function with the prototype int maximum( int x, int y, int z ); • Takes in 3 ints • Returns an int • Promotion rules and conversions • Converting to lower types can lead to errors KIC/Computer Programming & Problem Solving

  18. Function Prototypes KIC/Computer Programming & Problem Solving

  19. ExampleWrite a program that prints the following consider output numbers resulting from the mathematical relationship KIC/Computer Programming & Problem Solving

  20. Exampleoutput program KIC/Computer Programming & Problem Solving

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