1 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables

2 Administration Teaching assistant: Assaf Zaritsky Course’s home page: Office hours: Tuesdays, 15:10-16:10, Shenkar-Physics Building, room 406, or scheduled via /phone Office phone:

3 Grades Assignments: 20% Exam: 80%

4 Web Site Contact information Announcements All relevant material (homework, solutions, code examples, slides, etc…)

5 Homework Weekly homework assignments Programming assignment Each assignment is due in one week 20% of final grade Computer lab 06, open: 8:00 – 20:00, use /disk-on-key See submission guidelines for detailssubmission guidelines

6 Submission Guidelines Submission in singles! Hard-copy submission during practice or to my mail box (252) in the Schreiber building (second floor, in front of the elevator) Include example execution output Do not forget your ID Extensions Should work on Microsoft Dev Studio Pay careful attention to the guidelines

7 Agenda Administration Background Our first C program Working environment Memory and Variables

8 Basic Computer Model CPU (central processing unit) Input Output Memory Mouse, keyboard, hard disk… Printer, screen, hard disk…

9 Computer Program A sequence of processor instructions designed to achieve a specific purpose The instructions are executed sequentially. No instruction is executed before the previous has been completed

10 Machine Language Computers understand only machine language Basically looks like a sequence of 1’s and 0’s. Very inconvenient to work with and non intuitive. All other computer languages were created for human convenience The computer does not understand C Must be “translated” into machine language

11 Computer Languages Assembly – machine language with some text codes (still inconvenient). Compiled languages – C, Pascal, Fortran. The program is translated into machine language before execution

12 C is a Procedural Language It enables the user to create new instructions (procedures) from existing ones. Instead of re-writing the same code over and over again, write it once and call it when needed.

13 How do we compile? A special program – the “compiler” – “translates” from computer language to machine language There are many compilers on the market We will work with Microsoft Visual C++ 6.0

14 The Whole Process Write a program Your favorite text editor Compile + link the program C compiler will do one of two things: print error messages and abort (most probably…) produce an executable program Run the program

15 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables

16 C Program Template #include int main() { // Program’s “body” return 0; }

17 This is a comment – starts with a /* and ends with a */. Comments are used to explain the program to a human reader, and are ignored by the compiler. Curly braces indicate the beginning and end of a block of instructions. Specifically in this case – a function. This is an instruction to the compiler to insert the contents of the file stdio.h to the program prior to compilation. This file contains information about the printf fuction. Yet another C statement. This one terminates the program and informs the operating system that it has ended successfully. This tells the compiler we are about to define a function named main. main is a special function – it is where the program starts running. This is a C statement. This statement calls a function called printf, which causes text to be printed on the screen. Note that all C statements end with a semicolon (;). Our first C Program /* HelloWorld – An example program */ #include int main() { printf(“Hello, world!\n”); return 0; }

18 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables

19 Using Microsoft Visual c++

20 (Free) Visual Studio Express Free work environment Can be used from home Download and usage details can be found herehere

21 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables

22 Exercise Write, compile and run a program that prints your first name in one line, and your second name in another

23 A name printing program /* This program prints my name on the screen in two lines. */ #include int main() { printf(“Assaf\nZaritsky\n”); return 0; }

24 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables

25 Memory

26 Memory (Cont.) The computer memory is composed of a long list of bits Bits are grouped into bytes and words Every byte is numbered sequentially This number is called an address

27 What are variables? A named area in the computer memory, intended to contain values of a certain kind (integers, real numbers, etc.) Contain the data your program works with Can be used to store data to be used elsewhere in the program In short – they are the only way to manipulate data

28 Declaring Variables int num; int num1, num2; num = -1; // assignment int x = 9; // declaration + assignment int y = x + num; // y equals 8

29 Declaring Variables in C Before using a variable, one must declare it The declaration first introduces the variable type, then its name When a variable is declared, its value is undefined