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ModularityIn “C”

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What is Modularity? Modularity, is the heart of the high level, structured

languages. Means breaking down a big problem into smaller

parts, and writing code for each part. In C, modularity is implemented by using Functions.

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Advantages: Reduces complexity, Adds to clarity of the program, Provides reusability, Reduces redundant code, Makes it easier to maintain and modify the code in

future.

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Modularity in C: Modularity is accomplished by functions in “C”. A “C” program is a group of one or more functions. A “C” program MUST have at least one function

named main(). In C, execution begins with the main() function. There is a rich collection of built in functions that are

grouped in the “C” standard libraries.

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What is a function? Is a segment of code that accomplishes some task. It has a name, ex: pow. It has a body, which is “C” statements enclosed in

{ }. It may require 0 or more information (input(s)), It normally generates one result (output).

Inputs OutputFunction XXX

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Built in functions:

Include the proper header file in your C program.

Ex: scanf():

Is a built in function, #include <stdio.h> Requires 2 or more input

printf()

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math.h Appendix-B

To use the math library functions: #include <math.h>Ex: pow (12, 2) 144 sqrt (100) 10 abs (-23) 23

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Writing your own functions: Do not do it if there is a built in function.

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General Syntaxdata_type function_Name (parameter list)

{…return expression; // return output

}

Body of the function is a compound statement

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Parameter list:

A function gets the input data through its parameters.

Each parameter is a pair of: data type name

Input output

parametersFunction …

////

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Reture_typeReturn_type function_Name (parameter list)

{ …return expression; // return this exp.

}

Is the data type of the function’s result (output).

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return statement:Return_type function_Name (parameter list)

{…return exp; // return output

} A function sends out its result (output) via return

statement. Function’s output must be of the same data type as

Return_type .

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Cont… return expression:

expression can be a variable name, expression can be an expression that

evaluates to the proper data type.

Input outputreturn …

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Example-1: Write a function to display your information

to the screen: Think about:

Function’s name: display_myinfo Required input: none Produced output: none Task: To display: name and ssno to standard

output.

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void Means nothing! Use keyword void to indicate:

no input no output

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Write the code:void display_myinfo ()

{ printf (“Programmer: Good student \n”);

printf (“ID: 123-23-2323 \n”);

printf (“Course: CIT105 \n”);

}

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Invoke the function display_myinfo from main(): main() {

display_myinfo();}

See computer demo

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Example-2:

Write a function to compute the volume of a square box: Function name? Input data? Generated output?

Input? Output?

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Develop an algorithm:1) Declare variables2) Compute the volumne3) Return the result.

// See computer demo

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How to use a function? You must invoke it.

Specify its name, Send required data in, Store the produced output in a variable.

Function invocation appears either: On the right hand side of an assignment statement, Or can be part of an expression.

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Ex: Write a C program and use your function to compute the volume of a cube:#include <stdio.h>

float computeVolume (float side){ float volume; volume = side * side * side; return volume; }

Dummy name

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// main() function: main(){ float length, vol; printf(“ Enter side of the cube:”); scanf (“%f”, &length);

// Invoke the function, store the result in vol: vol = computeVolume( length);

// display the output: print f(“volume is = %f “, vol);}