Functions and Top-Down Design
in C
Top-Down Design with Functions
This lesson focuses on functions and their use in writing modular programs.
Chapter Objectives
The primary objective is to understand functions and how they facilitate the
creation of programs with distinct modules.
Case Studies
Two case studies are presented: finding the area and circumference of a
circle, and computing the weight of a batch of flat washers. The circle
example contrasts a non-modular implementation with a modular one. The
flat washer example uses a formula to compute the rim area.
Additional Operators and Functions
Some operations require functions beyond predefined operators. A function
is a program unit performing a specific operation, acting as a "black box"
where only inputs and outputs are known.
Square Roots and Math Functions
Square roots in C are computed using a function from the math library.
Math functions can be integrated into C statements and expressions, such as
z = a + sqrt(b-c);. All math functions accept and return values of type
double. For example, double x=100; printf ('The square root of
%0.1lf is %0.1lf', x, sqrt(x)); will output "The square root of 100.0
is 10.0".
Other Math Functions
Several other math functions are available:
y=floor (x): returns the largest whole number less than or equal to x.
y=fabs(x): returns the absolute value of x.
sin(x), cos(x), and tan(x): trigonometric functions that return the
sine, cosine, and tangent of an angle in radians. Radians can be
calculated from degrees using the formula: radians = degrees *
PI / 180;
y = exp (x): returns e to the power of x.
z = pow (x,y): returns x to the power of y.
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