2.1: Introduction

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In this exercise we will be taking a closer look at the Standard I/O functions printf() and scanf(). We shall also investigate the use of multiple user functions and prototypes. Further, we shall investigate the importance of proper program specification as well as choosing proper variable types.

This exercise involves creating a program that will assist with a simple series DC circuit analysis given component tolerances. Suppose that we have a circuit consisting of a DC voltage source and a resistor. We are interested in determining the resultant current through the circuit and the power dissipated by the resistor. This is a fairly straightforward exercise involving just Ohm’s Law and Power Law. To make this a little more interesting, we will include the effects of resistor tolerance. The program will create a table of currents and powers for the nominal, maximum and minimum allowed resistance values. This would be a very useful program for someone just starting their electrical studies. Let us keep this in mind while we design the program.

When designing a program, try to keep the user interaction as simple and as clear as possible. Also, try to structure the code to facilitate maintenance. Studies have shown that majority of programming time spent on non-trivial applications is in the area of maintenance (adding features, fixing bugs, etc.). Strive to make your code as clear as glass and include appropriate comments. Do not, however, add comments to code that even a novice would understand as that just creates clutter. Here is an example of bad commenting:

a = b + c;  /* add b to c */

Duh! This comment adds nothing to the quality of the code. Similarly, use mnemonic variable names where possible. This helps to create self-commenting code. Here is an example:

x = y + z * 60;
total_seconds = seconds + minutes * 60;

These two lines of code perform the same mathematical operations, but the second line gives you a hint as to what is intended. The first line would probably need a comment to make sense of it while the second line stands by itself.