[C] Variables and Arithmetic Expressions

Last Updated on 2021-04-29 by Clay

The most important function of computer invented is to assist humans in computing. So, in this section, we use the conversion between Celsius (°C) and Fahrenheit (°F) to explain which is variable and which is an arithmetic expression.

If fact, this is not a complicated concept. The so-called "variable" is a name that allows us to store a specific value.

For example:

int x = 10;

That means the variable x is assigned the value 10. We can use printf() to print the value of x any time.

The arithmetic expression is the calculation of:

• + : addition
• - : subtraction
• * : multiplication
• / : division

Conversion of Celsius (°C) and Fahrenheit (°F)

The conversion formula of Celsius (°C) and Fahrenheit (°F) is as follows:

And if it is expressed in a program, it can be written as:

#include <stdio.h>            


int main() {
    float F, C;
    int lower = 0;
    int upper = 300;
    int step = 20;

    // While
    F = lower;
    while (F <= upper) {
        C = (5.0 / 9.0) * (F - 32.0);
        printf("%3.0f %6.1f\n", F, C);
        F = F + step;
    }

    return 0;
}

Output:

  0  -17.8
 20   -6.7
 40    4.4
 60   15.6
 80   26.7
100   37.8
120   48.9
140   60.0
160   71.1
180   82.2
200   93.3
220  104.4
240  115.6
260  126.7
280  137.8
300  148.9

Here is a brief description of the meaning of each variable:

Then we use the while-loop to make F continue to execute before it is less than or equal to upper (The Maximum temperature boundary); in addition to using the formula to convert to C, don't forget to add F to the bottom of the block every time it is executed up 20 degrees.

If the temperature is not allowed to increase, the while-loop will be executed endlessly, which is probably not the result we want to see.

(Optional) printf() print variable specification

When using printf() to print variables, we can determine the specifications of the variables to be printed. For example: %6f means at least 6 characters width, %.2f means at least two decimal points but the width is not limited. Of course, %f is to print a floating point.

References

• http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/learninglabs/9780134309361/ch03.html
• https://www.tutorialspoint.com/format-specifiers-in-c

Read More

• [TOP ARTICLE] coding-interview-university Study Notes Directory
• [C] Use gcc command to compile and print "Hello World"