**12.010
Lecture 08 Exercises.**

In this section, we test and evaluate some
of the basic C concepts.

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Start with program hello.c. This program simply performs IO to print out a character string and the standard values of various numerical parameters from the C library.

To compile the program use the command

*cc hello.c*

To run the program use

*a.out*

Now edit the program to stop the header file
math.h from being included e.g.

*/* #include <math.h> */*

and recompile the code. What happens?

Look in the math.h header file
(/usr/include/math.h). Try printing out some of the

other mathematical constants. Printout
value for five different constants. What values do they have?

When
program area.c is invoked as follows

a.out 2.3

it is
supposed to calculate the area of a circle with radius 2.3. However, when you

compile and run the program it will print out 0. as the area of the circle.
What is wrong how can it be fixed?

Secondly, modify area.c so that it can take if several
radii and write one line

of out for each value stating the radius and the area of the circle with that
area.