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Senem Kumova Metin CS115 Introduction to Programming Inst. Senem Kumova Metin Textbook : A Book on C, A. Kelly and I.Pohl Lecture.

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Presentation on theme: "Senem Kumova Metin CS115 Introduction to Programming Inst. Senem Kumova Metin Textbook : A Book on C, A. Kelly and I.Pohl Lecture."— Presentation transcript:

1 Senem Kumova Metin 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

2 Senem Kumova Metin WHAT is LANGUAGE ?

3 Senem Kumova Metin 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

4 Senem Kumova Metin WHAT is a PROGRAMMING LANGUAGE ? A set of rules, symbols, and special words used to construct a computer program

5 Senem Kumova Metin 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 )

6 Senem Kumova Metin 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.

7 Senem Kumova Metin FLOW OF CONTROL 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 YESNO x = y+1 x = y-1 print x

8 Senem Kumova Metin 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… ….01 YESNO 10…

9 Senem Kumova Metin 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.

10 Senem Kumova Metin 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.

11 Senem Kumova Metin 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: 1. Interpretation, and 2. Compilation

12 Senem Kumova Metin 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.

13 Senem Kumova Metin 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

14 Senem Kumova Metin 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.

15 Senem Kumova Metin 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++…..

16 Senem Kumova Metin A SHORT BREAK ! 20 min …

17 Senem Kumova Metin INTRODUCTION TO C Your First C programs Basic I/O functions : printf / scanf Including libraries Writing comments Defining variables …. if statements

18 Senem Kumova Metin Learn printf #include // library file void main(void) { printf("from sea to shining C\n"); }

19 Senem Kumova Metin Learn printf #include void main(void) { printf("from sea ”); printf(“to shining C\n"); }

20 Senem Kumova Metin Learn printf / scanf #include 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); }

21 Senem Kumova Metin Comments /* Ignored part by the compiler */ // Ignored part by the compiler (only this line) void main() { //….. }

22 Senem Kumova Metin Comments Comments are arbitrary strings of symbols placed between the delimiters /* and */ Comments are not tokens but white spaces for the C compiler d) /*************/ /* a comment */ /*************/ b) /* * a comment */ c) /********** * a comment * ************/ a) /* a comment */

23 Senem Kumova Metin Variables and Assignment #include 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 }

24 Senem Kumova Metin Variables and Assignment OUTPUT: Money is 13 lira 56 kurus Total kurus is 1356 kurus

25 Senem Kumova Metin The use of #define /* Lines starting with # are called preprocessing directives Preprocessor first changes all occurences of identifier PI to 3.14 */ #include #define PI 3.14 void main(void) { printf(“PI equals : %f\n”,PI); // %f is used for floating numbers }

26 Senem Kumova Metin If Statements 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 C CODE void main() { int x; int y; if( x>0) x=y+1; else x=y-1; printf(“%d”, x); }

27 Senem Kumova Metin if statements int mymaximum( int a, int b) { if(a>b) return a; else return b;} MISSION : Write a function called mymaximum that gets 2 integer values (as input parameters) and returns back the greater one

28 Senem Kumova Metin Functions and if statements #include 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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