1 Agenda Administration Background Our first C program Working environment Exercise Memory and Variables.
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Agenda
Administration Background Our first C program Working environment Exercise Memory and Variables
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Administration Teaching assistant: Assaf Zaritsky e-mail:assafzar@post.tau.ac.il Course’s home page: http://
www.cs.tau.ac.il/~assafzar Office hours: Tuesdays, 15:10-16:10,
Shenkar-Physics Building, room 406, or scheduled via email/phone
Office phone: 03-6409759
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Grades
Assignments: 20% Exam: 80%
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Web Site
Contact information Announcements All relevant material (homework,
solutions, code examples, slides, etc…)
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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 email/disk-on-key See submission guidelines for details
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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
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Agenda
Administration Background Our first C program Working environment Memory and Variables
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Basic Computer Model
CPU (central processing unit)Input Output
Memory
Mouse, keyboard, hard disk…
Printer, screen, hard disk…
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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
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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
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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
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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.
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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
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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
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Agenda
Administration Background Our first C program Working environment Exercise Memory and Variables
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C Program Template
#include <stdio.h>int main(){ // Program’s “body” return 0;}
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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 <stdio.h>int main(){ printf(“Hello, world!\n”); return 0;}
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Agenda
Administration Background Our first C program Working environment Exercise Memory and Variables
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Using Microsoft Visual c++
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(Free) Visual Studio Express
Free work environment Can be used from home Download and usage details can
be found here
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Agenda
Administration Background Our first C program Working environment Exercise Memory and Variables
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Exercise
Write, compile and run a program that prints your first name in one line, and your second name in another
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A name printing program
/* This program prints my name on the screen in two lines. */
#include <stdio.h>int main(){ printf(“Assaf\nZaritsky\n”); return 0;}
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Agenda
Administration Background Our first C program Working environment Exercise Memory and Variables
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Memory
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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
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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
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Declaring Variables
int num; int num1, num2; num = -1; // assignment int x = 9; // declaration +
assignment int y = x + num; // y equals 8
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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
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