Introduction to programming language using c
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This document discusses functions in the C programming language. It covers function definitions and prototypes, different types of function calls including call by value and call by reference, storage classes, scope rules, recursion, and examples using math library functions and random number generation. The document is part of a course on introduction to programming using C at Trinity Institute of Professional Studies in New Delhi, India.
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Introduction to programming language using c
- 1. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Affiliated Institution of G.G.S.IP.U, Delhi INTRODUCTION TO PROGRAMMING LANGUAGE USING C Topic: Functions Paper Id: 20105 Paper code: BCA 105
- 2. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Functions Outline 1 Introduction 2 Program Modules in C 3 Math Library Functions 4 Functions 5 Function Definitions 6 Function Prototypes 7 Header Files 8 Calling Functions: Call by Value and Call by Reference 9 Random Number Generation 10 Example: A Game of Chance 11 Storage Classes 12 Scope Rules 13 Recursion 14 Example Using Recursion: The Fibonacci Series 15 Recursion vs. Iteration
- 3. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 • 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 Introduction
- 4. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Program Modules in C • 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
- 5. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 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
- 6. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Functions • Functions – Modularize a program – All variables declared 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
- 7. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 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
- 8. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Function Definitions • Function definition format (continued) return-value-type function-name( parameter-list ) { declarations and statements } – Declarations and statements: function body (block) • Variables can be declared 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 – return expression;
- 9. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 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, int, int ); • Takes in 3 ints • Returns an int • Promotion rules and conversions – Converting to lower types can lead to errors
- 10. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Header Files • Header files – Contain function prototypes for library functions – <stdlib.h> , <math.h> , etc – Load with #include <filename> #include <math.h> • Custom header files – Create file with functions – Save as filename.h – Load in other files with #include "filename.h" – Reuse functions
- 11. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Calling Functions: Call by Value and Call by Reference • Used when invoking functions • Call by value – Copy of argument passed to function – Changes in function do not effect original – Use when function does not need to modify argument • Avoids accidental changes • Call by reference – Passes original argument – Changes in function effect original – Only used with trusted functions • For now, we focus on call by value
- 12. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Random Number Generation • rand function – Load <stdlib.h> – Returns "random" number between 0 and RAND_MAX (at least 32767) i = rand(); – Pseudorandom • Preset sequence of "random" numbers • Same sequence for every function call • Scaling – To get a random number between 1 and n 1 + ( rand() % n ) • rand() % n returns a number between 0 and n - 1 • Add 1 to make random number between 1 and n 1 + ( rand() % 6) – number between 1 and 6
- 13. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Random Number Generation • srand function – <stdlib.h> – Takes an integer seed and jumps to that location in its "random" sequence srand( seed ); – srand( time( NULL ) ); //load <time.h> • time( NULL ) – Returns the time at which the program was compiled in seconds – “Randomizes" the seed
- 14. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Storage Classes • Storage class specifiers – Storage duration – how long an object exists in memory – Scope – where object can be referenced in program – Linkage – specifies the files in which an identifier is known (more in Chapter 14) • Automatic storage – Object created and destroyed within its block – auto: default for local variables auto double x, y; – register: tries to put variable into high-speed registers • Can only be used for automatic variables register int counter = 1;
- 15. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Storage Classes • Static storage – Variables exist for entire program execution – Default value of zero – static: local variables defined in functions. • Keep value after function ends • Only known in their own function – extern: default for global variables and functions • Known in any function
- 16. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Scope Rules • File scope – Identifier defined outside function, known in all functions – Used for global variables, function definitions, function prototypes • Function scope – Can only be referenced inside a function body – Used only for labels (start:, case: , etc.)
- 17. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Scope Rules • Block scope – Identifier declared inside a block • Block scope begins at declaration, ends at right brace – Used for variables, function parameters (local variables of function) – Outer blocks "hidden" from inner blocks if there is a variable with the same name in the inner block • Function prototype scope – Used for identifiers in parameter list
- 18. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Recursion • Recursive functions – Functions that call themselves – Can only solve a base case – Divide a problem up into • What it can do • What it cannot do – What it cannot do resembles original problem – The function launches a new copy of itself (recursion step) to solve what it cannot do – Eventually base case gets solved • Gets plugged in, works its way up and solves whole problem
- 19. TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75 Recursion • Example: factorials – 5! = 5 * 4 * 3 * 2 * 1 – Notice that • 5! = 5 * 4! • 4! = 4 * 3! ... – Can compute factorials recursively – Solve base case (1! = 0! = 1) then plug in • 2! = 2 * 1! = 2 * 1 = 2; • 3! = 3 * 2! = 3 * 2 = 6;