Slide 1: A bit of C programming

Lecture 3

Uli Raich

Slide 2: Programming Languages

To make a language a programming language it needs to implement:

• Assignments
• Conditional statements
• loops

Slide 3: C libraries

C uses a large number of code libraries and you can create C libraries yourself.

These libraries may use special data types, which are defined in include files

Before using the library functions

#include <stdio.h>

or

#include “myOwnIncludeFile.h”

Slide 4: The C main program

As a first example people usually write the

“Hello World” program

Let us try to compile and execute this program

First we start the editor, we type and save the program,

then we compile it using the gcc compiler and finally we execute it.

Slide 5: C data types

• C has a number of data types:
• char, short, int, long, float, double
• unsigned char, unsigned short, unsigned int
• can be extended to boolean (in C99 you can #include <stdbool.h>
• No strings! But a pointer to a zero terminated chain of characters
• struct
• union
• enum

Slide 6: Assignments

We modify the program to do some calculation:

Slide 7: Conditions: the if statement

Conditions can be tested with if

if (a < b)

printf(“a is bigger than b\n”);

else

printf(“b is bigger than a\n”);

Slide 8: Calculating the Fibonacci numbers

The Fibonacci numbers:

0 1 1 2 3 5 8 13 21 34 …

or xn = xn-1+xn-2

How can we write a program to calculate up to 12 such numbers?

This can easily be done in a for loop

Slide 9: The for loop

Slide 10: The while loop

Can we also do calculations as long as the Fibonacci number

does not exceed a certain value?

Slide 11: Pointers

We can define variables which do not contain the value but

the address of where the value is stored in memory:

char a=5; is the value

char *myText=”Hello World!”;

myText points to the place in memory where Hello World is stored.

Slide 12: Pointer Example

Slide 13: Command line arguments

The main routine has 2 parameters, which we did not use

yet as well as a return code.

int main(int argc, char ** argv) or

int main(int argv, char *argv[ ]);

int argc is the number of arguments passed

char **argv is a pointer to a list of null terminated C strings.

Slide 14: Command line arguments example

-- Uli Raich - 2017-09-07

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