1. CS115 Introduction to Programming
Inst. Senem Kumova Metin
Textbook : A Book on C, A. Kelly and I.Pohl
Lecture Notes :
Office hours : TBA
Office : 408
Senem Kumova Metin

2. WHAT is LANGUAGE ?
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3. WHAT is PROGRAMMING?? scheduling or performing a task or / and event WHAT is COMPUTER PROGRAMMING?? creating a sequence of steps for a computer to follow in performing a task
Senem Kumova Metin

4. WHAT is a PROGRAMMING LANGUAGE ?
A set of rules, symbols, and special words used to construct a computer program
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5. Programming language rules consist of:
Rules of Syntax which specify how valid instructions are written in the language (like natural language rules subject + verb +object )
Rules of Semantics which determine the meaning of the instructions (what the computer will do) (like natural language rules A book has bitten a car )
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6. A COMPUTER PROGRAM ?
A set of machine instructions which in turn are represented as sequences of binary digits ( … )
The execution sequence of a group of machine instructions is known as the flow of control.
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7. FLOW OF CONTROL x > 0 print x int x and int y x = y+1 x = y-1
SCENARIO :
you have 2 integers : x,y
if x is greater than 0 then
do x= y+ 1;
else
do x= y-1;
print the value of x
int x and int y
x > 0
YES NO
x = y+1
x = y-1
print x
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8. Will we write codes in binary ??
SCENARIO :
you have 2 integers : x,y
if x is greater than 0 then
do x= y+ 1;
else
do x= y-1;
print the value of x
000…110001
100010….01
YES NO
10…
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9. ASSEMBLY LANGUAGE
Assembly language (or assembler code) was our first attempt at producing a mechanism for writing programs that was more palatable to ourselves
movl #0x1,n
compare:
cmpl #oxa,n
cgt end_of_loop
acddl #0x1,n
bra compare
end_of_loop:
Of course a program written in assembly code, in order to “run”, must first be translated (assembled) into machine code.
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10. HIGH LEVEL LANGUAGE
From the foregoing we can see that assembler language is not much of an improvement on machine code!
A more problem-oriented (rather than machine-oriented) mechanism for creating computer programs would also be desirable.
Hence the advent of high(er) level languages starts with the introduction of “Autocodes”, and going on to Algol, Fortran, Pascal, Basic, Ada, C, etc.
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11. PROGRAM PROCESSING
A program written in a high level language (source code) can only be run in its machine code equivalent format.
SOURCE CODE  MACHINE CODE
There are two ways of achieving this:
Interpretation, and
Compilation
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12. 1. INTERPRETATION
Interpretation requires the use of a special program that reads and reacts to source code.
Such a program is called an interpreter.
During interpretation run-time errors may be detected and “meaningful” error messages produced.
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13. 2. COMPILATION
Compilation requires the use of a special program (called a compiler) that translates source code into object code.
SOURCE CODE  OBJECT CODE
Sometimes various library files must be “linked in” using another special program called a linker, which produces executable code.
OBJECT CODE  MACHINE CODE
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14. LIBRARIES
Libraries (in computer programming terms) contain chunks of precompiled (object) code for various functions and procedures that come with a programming language that requires compilation
For example functions and procedures to facilitate I/O.
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15. Why C? Native language of UNIX
Standard development language for personal computers
Portable (can be moved to other machine !)
Powerful set of operators and powerful libraries (some operators: ++,--….)
Basis for Java, C++…..
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16. A SHORT BREAK !
20 min …
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17. INTRODUCTION TO C Your First C programs
Basic I/O functions : printf / scanf
Including libraries
Writing comments
Defining variables ….
if statements
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18. Learn printf #include <stdio.h> // library file void main(void){
printf("from sea to shining C\n"); }
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19. Learn printf #include <stdio.h> void main(void) {
printf("from sea ”);
printf(“to shining C\n"); }
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20. Learn printf / scanf #include <stdio.h> void main(void) {
int x=0;
printf(“x= %d”,x); // print x = 0
scanf(“%d”,&x); /* scan the value from screen and assign this value to x */
printf(“%d”,x); }
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21. Comments /* Ignored part by the compiler */
// Ignored part by the compiler (only this line)
void main()
{ //….. }
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22. Comments
Comments are arbitrary strings of symbols placed between the delimiters /* and */
Comments are not tokens but white spaces for the C compiler
a) /* a comment */
c)   /**********    *  a comment *    ************/
b)    /*     * a comment     */
d)  /*************/      /*  a comment */     /*************/
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23. Variables and Assignment
#include<stdio.h>
void main(void) {
int kurus; // declarations of variables (int is a keyword, takes integer values)
int lira=0; // declaration and initialization of a variable
int toplam_kurus;
lira =13; // Assignment statement, “=“ is the assignment operator
kurus=56; // Assignment
printf(“ Money is %d lira %d kurus\n”, lira, kurus); // printf statement
toplam_kurus = lira*100+ kurus;
printf(“ \n Total kurus is %d kurus\n”, toplam_kurus);
// first part of the printf statement is a control string }
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24. Variables and Assignment
OUTPUT:
Money is 13 lira 56 kurus
Total kurus is 1356 kurus
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25. The use of #define #include<stdio.h> #define PI 3.14
/* Lines starting with # are called preprocessing directives
Preprocessor first changes all occurences of identifier PI to 3.14 */
#include<stdio.h>
#define PI 3.14
void main(void) {
printf(“PI equals : %f\n”,PI);
// %f is used for floating numbers }
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26. If Statements C CODE SCENARIO/ MISSION : void main()
{ int x; int y;
if( x>0)
x=y+1;
else
x=y-1;
printf(“%d”, x); }
SCENARIO/ MISSION :
you have 2 integers : x,y
if x is greater than 0 then
do x= y+ 1;
else
do x= y-1;
print the value of x
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27. if statements int mymaximum( int a , int b) { if(a>b) return a;
MISSION :
Write a function called mymaximum that
gets 2 integer values (as input parameters) and returns
back the greater one
int mymaximum( int a , int b)
{ if(a>b)
return a;
else
return b; }
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28. Functions and if statements
#include <stdio.h>
int mymaximum(int a, int b); // FUNCTION PROTOTYPE
void main(void)
{ int max, x, y =7; // DECLARE 3 VARIABLES, INITIALIZE Y
printf("please give the value for x: ");
scanf("%d",&x); // GET THE VALUE OF VARIABLE X
max= mymaximum(x,y); // CALL TO THE MYMAXIMUM FUNCTION
printf("Maximum = %d",max); // PRINT THE OUTPUT }
int mymaximum( int a , int b) // DEFINE SUB-FUNCTION
{ if(a>b) return a;
else return b; }
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