# Senem Kumova Metin // FALL 2008-2009 CS115 Introduction to Programming Inst. Senem Kumova Metin Textbook : A Book on C, A. Kelly.

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Senem Kumova Metin // FALL 2008-2009 CS115 Introduction to Programming Inst. Senem Kumova Metin senem.kumova@ieu.edu.tr Textbook : A Book on C, A. Kelly and I.Pohl Lecture Notes : http://homes.ieu.edu.tr/~skumova/ Office hours : TBA Office : 306

Senem Kumova Metin // FALL 2008-2009 WHAT is LANGUAGE ?

Senem Kumova Metin // FALL 2008-2009 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 // FALL 2008-2009 WHAT is a PROGRAMMING LANGUAGE ? A set of rules, symbols, and special words used to construct a computer program

Senem Kumova Metin // FALL 2008-2009 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 )

Senem Kumova Metin // FALL 2008-2009 A COMPUTER PROGRAM ? A set of machine instructions which in turn are represented as sequences of binary digits (0001010….111011) The execution sequence of a group of machine instructions is known as the flow of control.

Senem Kumova Metin // FALL 2008-2009 FLOW OF CONTROL SCENARIO : we 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

Senem Kumova Metin // FALL 2008-2009 Will we write codes in binary ?? SCENARIO : we 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 YESNO 10…1010000 1011..0101 100..11100010

Senem Kumova Metin // FALL 2008-2009 ASSEMBLY LANGUAGE Assembly language (or assembler code) was our first attempt at producing a mechanism for writing programs that was more palatable to ourselves ; the easiest way to print "hello, world!" name "hi" org 100h jmp start ; jump over string declaration msg db "hello, world!",0Dh,0Ah, 24h start: lea dx, msg ; load effective address of msg into dx. mov ah, 09h ; print function is 9. int 21h ; do it! mov ah, 0 int 16h ; wait for any key any.... ret ; return to operating system. Of course a program written in assembly code, in order to “run”, must first be translated (assembled) into machine code.

Senem Kumova Metin // FALL 2008-2009 HIGH LEVEL LANGUAGE 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.

Senem Kumova Metin // FALL 2008-2009 ASSEMBLY versus HIGH LEVEL LANGUAGE ; the easiest way to print "hello, world!" name "hi" org 100h jmp start ; jump over string declaration msg db "hello, world!",0Dh,0Ah, 24h start: lea dx, msg ; load effective address of msg into dx. mov ah, 09h ; print function is 9. int 21h ; do it! mov ah, 0 int 16h ; wait for any key any.... ret ; return to operating system. /* easiest way to print “hello, world” */ #include // library file main() {printf(“hello,world”); } HelloWorld.asmHelloWorld.c

Senem Kumova Metin // FALL 2008-2009 ASSEMBLY versus HIGH LEVEL LANGUAGE HelloWorld.asm Source Code HelloWorld.c Source Code Machine Code (binary) Object Code assembled compiled Library (stdio.h) linked

Senem Kumova Metin // FALL 2008-2009 A typical C development environment 1/2 Phase1. Create a program Use some editor to create your.c file (emacs, vi, pico etc.) Save the file in disk.c file is known as source code Phase2 and 3. Preprocess and Compile Preprocessor manipulates program code (examples: includes other files, performs text replacements) Compiler generates.o file known as the object code Phase4. Linking Linker links the library files and creates executable file To compile your.c file type “gcc –c myfile.c”, this will create.o file To compile & link type “gcc –o myfile myfile.c” this will create myfile.exe file and executable myfile.exe

Senem Kumova Metin // FALL 2008-2009 A typical C development environment 2/2 Phase5. Loading Before a program can be executes, it must be first placed to memory by Loader Phase6. Execution Under control of CPU, a program may be executed To load and execute your.exe file type “./myfile”

Senem Kumova Metin // FALL 2008-2009 Compilation with gcc compiler in Linux && Execution Step1 : gcc –c myfile.c  myfile.c + myfile.o Step2 : gcc –o myfile myfile.c  myfile.c + myfile.o +myfile.exe Step3 :./myfile or Step1 : gcc –c myfile myfile.c  myfile.c +myfile.exe Step2 :./myfile You may use also cc compiler instead of gcc

Senem Kumova Metin // FALL 2008-2009 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.

Senem Kumova Metin // FALL 2008-2009 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++…..

Senem Kumova Metin // FALL 2008-2009 A SHORT BREAK ! 20 min …

Senem Kumova Metin // FALL 2008-2009 INTRODUCTION TO C Your First C programs Basic I/O functions : printf / scanf Including libraries Writing comments Defining variables …. if statements

Senem Kumova Metin // FALL 2008-2009 Learn printf #include // library file void main(void) { printf("from sea to shining C\n"); }

Senem Kumova Metin // FALL 2008-2009 Learn printf #include void main(void) { printf("from sea ”); printf(“to shining C\n"); }

Senem Kumova Metin // FALL 2008-2009 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); }

Senem Kumova Metin // FALL 2008-2009 Comments /* Ignored part by the compiler */ // Ignored part by the compiler (only this line) void main() { //….. }

Senem Kumova Metin // FALL 2008-2009 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 */

Senem Kumova Metin // FALL 2008-2009 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 }

Senem Kumova Metin // FALL 2008-2009 Variables and Assignment OUTPUT: Money is 13 lira 56 kurus Total kurus is 1356 kurus

Senem Kumova Metin // FALL 2008-2009 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 }

Senem Kumova Metin // FALL 2008-2009 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); }

Senem Kumova Metin // FALL 2008-2009 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

Senem Kumova Metin // FALL 2008-2009 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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