Unit 5

Modular Programming

Key Concepts

• Input parameters• Output parameters• Pointers• Multiple functions• Identifier scope• Types of testing

Functions with Input Parameters• Data is passed into the function, but

cannot be modified by the function.• Example:

double getCircum(double radius){

return (2 * PI * radius);}int main(void){ double circum, r;

r = 20; circum = getCircum(r);}

Output Parameters

• Allow a function to modify the value of one or more address locations

• Are parameters defined as pointers to the address location

• Example:int *wholep;– Points to the location in memory where the

function will store a value

Calling a Function with Output Parameters

• Use the address of operator (&) before the name of the variable.

• Example:separate(value, &sn, &whl, &fr);

Figure 6.2

Diagram of Function separate with Multiple Results

Figure 6.1

Function separate

Figure 6.3

Program That Calls a Function with Output Arguments

Figure 6.3 Program That Calls a Function with Output Arguments (cont’d)

Figure 6.3

Program That Calls a Function with Output Arguments (cont’d)

Figure 6.4

Parameter Correspondence for separate(value, &sn, &whl, &fr);

Effects of & Operator on the Data Type of a Reference

Table 6.1

Figure 6.5

Comparison of Direct and Indirect Reference

Figure 6.6 Program to Sort Three Numbers

Figure 6.6 Program to Sort Three Numbers (cont’d)

Tracing the Sorting Program

Table 6.2

Figure 6.7 Data Areas After temp = *smp;

During Call order(&num1, &num3);

Scope of Names

• Constant macros can be used from any line of code after they are referenced

• Functions can be accessed any time after their prototype unless their name is "shadowed" by a function parameter with the same name

• Formal parameters and variables defined in a function can only be accessed within that function

Figure 6.8 Outline of Program for Studying Scope of Names

Scope of Names in Figure 6.8Table 6.4

Passing an Output Parameter as an Argument

• An output parameter is a pointer to a memory location

• To pass it to a function as an output parameter, pass it without an operator:void scan_fraction (int *nump, int *dnomp)

{ char slash; slash = '/' scanf("%d %c%d", nump, &slash, dnomp);

}

Figure 6.9

Function scan_fraction (incomplete)

Figure 6.9

Function scan_fraction (incomplete) (cont’d)

Figure 6.10

Data Areas for scan_fraction and Its Caller

Figure 6.11

Structure Chart for Common Fraction Problem

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions (cont’d)

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions (cont’d)

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions (cont’d)

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions (cont’d)

Figure 6.12

Program to Perform Arithmetic Operations on Common Fractions (cont’d)

Figure 6.13

Sample Run of a Partially Complete Program Containing Stubs

Top-Down vs. Bottom-Up TestingTop-down testing• Create function stubs to

test the main program.• Add each function as it is

complete and retest.

Bottom-up testing• Separately test each

function before integration.

• Create a driver to test the function.

• Unit testing – testing a function

• Integration testing – testing the complete program after all functions have been added

Figure 6.14

Stub for Function multiply_fractions

Figure 6.15

Driver for Function scan_fraction