Computer Programming I

Computer Programming I UP ITTC AY 2009-2010

Computer Programming I Introduction: Computer Programming Lesson 1: Overview of Programming Languages
Lesson 2: Introduction to C Programming
Lesson 3: C Fundamentals
Lesson 4: Control Structures


Computer Programming I Lesson
Lesson
Lesson
Lesson
Lesson
Lesson


5: Subprograms 6: Arrays, Strings and Pointers 7: Command-Line Arguments 8: Structures 9: Dynamic Memory Allocation 10: File Handling

Preface


Prerequisites Computer

Systems 1 Knowledge of algorithms


Related Publications The


C

C Programming Language 2nd Edition

Brian W. Kernighan, Dennis M. Ritchie

by Dissection 4th Edition


Al Kelly, Ira Pohl

Overview


This course introduces computer programming using the language C.

Objectives At the end of this course, you should be able to:
Understand the methodology for implementing a program.
Understand the programming elements involved in implementing a program in C.
Understand the creation and reuse of parts of a program.

Duration



Lecture: 24 hours (4 days) Workshop: 36 hours (6 days)

Schedule Day 1
Lesson 1: Overview of Programming Languages
Lesson 2: Introduction to C Programming
Lesson 3: C Fundamentals

Schedule Day 2



Lesson 5: Control Structures Lesson 6: Subprograms

Schedule Day 3




Lesson 8: Array, Strings and Pointers Lesson 9: Command-Line Arguments Lesson 10: Structures

Schedule Day 4



Lesson 10: Dynamic Memory Allocation Lesson 11: File Handling

Schedule Days 5 - 7:  Workshop:

Machine Problem Part 1

Days 8 – 10:  Workshop:

Machine Problem Part 2  Departmental Exam

Course Requirements





Machine Exercises Machine Problem Part 1 Machine Problem Part 2 Long Exam (Departmental Exam)

20% 20% 30% 30%

Overview of Programming Languages Lesson 1

Introduction



Definition of Programming Languages Levels of Programming Languages  Machine

Language  Assembly Languages  High-level Languages  Very High-level Languages  Natural Languages

What is a Programming Language?


A programming language is a set of rules for instructing the computer what operations to perform.

Levels of Languages






Machine Language Assembly Languages High-level Languages Very High-level Languages Natural Languages

Machine Language


Machine language is the only language understood by a computer




Consists of binary numbers (1s and 0s)

Assembly Languages





Assembly language is a low level message which uses mnemonic codes and abbreviations that are easy to remember We use an assembler in order to convert it from assembly language to machine language

High-level Languages






High-level languages are programming languages that are written in English-like manner. Examples: C, C++, Java, Pascal We use a compiler in order to convert it to machine language.

Very High-level Languages


Very high-level languages are essentially shorthand programming languages.




Also called fourth-generation languages or 4GLs.

Lesson Review











A programming language is a set of rules for instructing the computer what operations to perform. There are five generations/levels of languages: Machine Language, Assembly Languages, Highlevel Languages, Very High-level Languages and Natural Languages. An assembler is used to convert assembly language to machine language. A compiler is used to convert a high-level language to machine language.

Introduction to C Programming Lesson 2

Introduction







Introduction to C Characteristics of C Elements of a C Program Our First C Program: Hello World Compiling & Running our first C Program Phases of a C Program

The “C” Programming Language


A high-level general-purpose programming language




Developed by Brian Kernighan and Dennis Ritchie of AT&T Bell Labs in 1972

Characteristics of C








C is a small language. C is the standard development language for personal computers. C is portable. C is modular. C is the basis for C++ and java.

Elements of a C Program


Identifiers a

name in a C program  a string of letters, digits and underscores, provided that the string doesn’t start with a digit.  Case-sensitive  Examples of VALID identifiers _hello IamAnIden1234 _1234  Example of INVALID identifiers 123hello dDAT.1 file-name

Elements of a C Program


Reserved Words/Keywords words that have predefined meanings and cannot be used as names for anything else.  C has 32 keywords, these are: 

Our First C Program /** * Hello.c * This is my very first C program and I'm * excited about it :-) **/ #include <stdio.h> int main( void ) { /*print text to screen*/ printf("Hello world!"); }



This is a Comment. Comments are used for documentation purposes and does not affect the program flow.

Our First C Program 

/** * Hello.c * This is my very first C program and I'm * excited about it :-) **/ #include <stdio.h> int main( void ) { /*print text to screen*/ printf("Hello world!"); }

Our First C Program 



This is a Preprocessor or Precompiler directive. A Preprocessor or Precompiler directive are lines in C that are processed before compiling the code.

/** * Hello.c * This is my very first C program and I'm * excited about it :-) **/ #include <stdio.h> int main( void ) { /*print text to screen*/ printf("Hello world!"); }

Our First C Program Define a block of commands called main.  main is a special block – it is where the program starts Crunning. program and I'm  Every C program must have a single main block. 

/** * Hello.c * This is my very first * excited about it :-) **/ #include <stdio.h>

int main( void ) { /*print text to screen*/ printf("Hello world!"); }

Our First C Program /** * Hello.c * This is my very first C program and I'm * excited about it :-) **/ #include <stdio.h> int main( void ) { /*print text to screen*/ printf("Hello world!"); }



This is also a comment.

Our First C Program The printf function is a standard output function which takes in a string as its function argument, and it to theand screen.I'm Coutputs program
This is an example of a statement, it ends with a semicolon.


/** * Hello.c * This is my very first * excited about it :-) **/ #include <stdio.h>

int main( void ) { /*print text to screen*/ printf("Hello world!"); }

Compiling our first C Program


Compiler Used to convert a high-level language to machine language  gcc – name of the compiler we will use to compile our C programs 

Phases of C Programs: 

    

Edit (C program file names should end with the .c extension) Preprocess Compile Link Load Execute

Phases of C Program









Phase 1: Create your program with an editor program Phase 2: A preprocessor find some preprocessor directives (#include <stdio.h>) to include other files and perform various text replacements Phase 3: Compiler compiles the program into machine languages (object code != object-oriented programming). Phase 4: A linker links the object code with the code in library or other places to produce an executable image. Phase 5: A loader loads the executable image into memory (RAM). Phase 6: CPU executes the program one instruction at a time.

Lesson Review








C is a high-level general-purpose programming language developed by Brian Kernighan and Dennis Ritchie of AT&T Bell Labs in 1972. Identifiers are names in a C program. It consists of a string of letters, digits and underscores, provided that the string doesn’t start with a digit. It is case-sensitive. Reserved words or keywords in C, are words that have predefined meanings and cannot be used as names for anything else. C has 32 keywords.

Lesson Review


To compile: gcc -o




To run: ./




6 phases that a C program undergoes: Edit, Preprocess, Compile, Link, Load and Execute

Exercise 1


Write a short but complete C program that outputs to screen what you feel about your instructor.

C Fundamentals Lesson 3

Introduction
C

Program Structure

  

Preprocessor/Precompiler directives Libraries Declarations





Type declarations Variable/constant declarations Function/procedure declarations Main function declarations

Introduction







Statements and Blocks Basic Data Types Constants Variables Basic I/O: scanf, printf Operators  Arithmetic, Increment/Decrement, Relational, Logical, Modulo, Assignment, Shortcut  Precedence

C Program Structure Program structure for C programs: [<preprocessor/precompiler directives>] [<declarations>] <main-function-definition> []

Preprocessor / Precompiler Directives







Precompiler directives or preprocessors are statements in C that are processed before compilation. Usually begins with the # symbol perhaps preceded by white spaces. They may appear anywhere. Examples: #include.. #define...

Libraries
a

collection of useful functions and symbols that may be accessed by a program
has a standard header file whose name ends with the symbols .h
Example: #include <stdio.h> definitions*/

/*printf, scanf

Declarations The following are different types of declarations in C: | |

Variable/Constant Declarations
The

syntax of a variable/constant declaration is: [const] [= ];

Variable/Constant Declarations
Declarations

that begin with const are constant declarations while those that do not are variable declarations.
Examples: const age_type age = 22; const float salary = 54321.20; char* name, address; char gender = 'M';

Function/Procedure Declarations
The

syntax of a function/procedure declaration is: (<parameters>) { }

Function/Procedure Declarations
Declarations

whose return type is void are procedure declarations. Otherwise, they are function declarations.
Examples: void greet(void){ printf("Hello there.\n");

} int add(int x, int y){ return x+y;

}

Main Function Declaration
The

syntax of the main function declaration is: main (<parameters>){ <main_body> }

Sample Program

C Statements & Blocks
C

Statements are lines of code ending with a semicolon (;).


Blocks

are groups of statements enclosed in curly braces {}.

Basic Data Types
C

has at least 3 basic data types:

  

Character (char) Integer (int) Floating point numbers (float/double)

Character Data Type
A

character in C is in the form: '<single character>'


Examples: 'a' (letter a) ':' (colon) '*' (asterisk) 'T' (capital T)

'1' (number one) ' ' (space) '?' (question mark)

Character Data Type
C

has special kinds of characters called escape sequences.
Here are some of the escape sequences in C: '\f' (formfeed) '\\' (backslash) '\n' (newline) '\'' (single quote) '\r' (carriage return) '\"' (double quote) '\t' (horizontal tab) '\ooo' (octal number) '\xhh' (hexadecimal number)

Character Data Type
Are  

really just integers.

Character encoding is platform specific. ASCII, Unicode, ISO 8859


char 

At least 8 bits (“byte”)


wchar_t  

“Wide character” Usually the same as unsigned int (Unicode)

The ASCII Table

Integer Data Type




Integers have values that are whole numbers. They can be positive or negative. The type name for integer data type in C is:

int


Can be written as:  Decimal -1234  Hexadecimal -0x1234  Octal -01234

230 0x0E6 0346

+250 +0xFA +0372

Floating Point Data Type
A

floating point in C is the data type whose values are numbers, that, when written in the usual decimal notation, have digits after the decimal point.
The type name for floating point data type in C is: float
Examples of floating points are: 1.0

0.31416 1E6

4.3E5

typedef
In

C, you can define your own data types based on existing data types. (alias)
Type declaration using basic data types has the following syntax: typedef ;

typedef
Examples:

typedef char gender_type; typedef int age_type; typedef float grade_type;

Constants
Constants

in C are values that never change throughout the entire program.
Types of Constants in C:     

Integer Character Floating-point String Enumeration

Constants
To

declare your own constants:

const = ;
Examples:

const char middle_initial = 'C'; const int num_colors = 7; const float pi = 3.1416;

Constants
You

can also use the #define preprocessor to declare constants in your program.
The syntax is: #define [value]
Examples:

#define Kg_Per_Lbs #define Pi

0.454545 3.1416

Variables
Variables,

in C, are objects whose value may change during the course of a program’s execution.


A

variable in C is declared using the following syntax: [= ];

Variables





Named area in the computer memory, intended to contain values of a certain kind (integers, real numbers, characters etc.) They contain the data your program works with

Variables Declaration





Before using a variable, one must declare it. Variables declaration may only appear at the beginning of a block. The declaration first introduces the variable type, then its name. When a variable is declared, its value is undefined.

Type

int float double char

integer; small_real; big_real; c1, c2;

Identifier

Variables Declaration
Naming 

Letters, digits, underscores







i CSE_5a a_very_long_name_that_isnt_very_useful fahrenheit

First character cannot be a digit




rules:

5a_CSE

is not valid!

Case sensitive


CSE_5a is different from cse_5a

Example: Variable Declarations int i, j; char ch; float num1 = 5.20, num2 = 7.0; double d;

Primitive Data Types











char – character (1 byte)  ‘a’, ‘b’, ‘c’ ..., ‘A’, ‘B’, ‘C’, ...  ‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ‘0’  ‘_’ ‘,’ ‘#’ ‘$’ ‘^’ ‘*’ ‘@’ ‘!’ .... int – integer number (4 bytes).  0, -1, 1, -2, 2, .... float – real number (4 bytes)  0.5, 3.2, 4.0, -5.122323, ... double – double precision real number (8 bytes) char

float

int

double

Basic output: printf
printf  

Allows you to print on the screen To print some string using printf, we type: printf("");

To print a value of a variable using printf, we use format specifiers:



printf("[format specifier]", variable);

printf Conversion Codes








%c – a character %d – an integer, %u – an unsigned integer. %f – a float %e – a float in scientific representation %g – whichever is better between %e and %f %lf – a double %% - the ‘%’ character

Basic output: printf
Example:

char letter = 'a'; int number = 100; float fnum = 13.09 printf("This is the letter %c", letter); printf("The number = %d", number); printf("This is a floating point number %f", fnum); printf("%c %d %f", letter, number, fnum);

Basic input: scanf
scanf 

Allows you to get input from the keyboard



Format: scanf( "", &variableName )

Basic input: scanf
Examples:

int number; char letter; printf("Enter a number:"); scanf("%d", &number); printf("Enter a character:"); scanf("%c", &letter);

scanf Conversion Codes








%c – a character %d – an integer, %u – an unsigned integer. %f – a float %e – a float in different representation %lf – a double

Exercise 2


Write a program that asks the user to input his/her name, age, address, telephone number and desired grade. Afterwards print all the information provided by the user.

Signed vs. Unsigned


integer types can be signed or unsigned unsigned int ui; unsigned char uc;




char  




signed: -128 to +127 unsigned: 0 to +255

int  

signed: −2,147,483,648 to +2,147,483,647 unsigned: 0 to +4,294,967,295

The unsigned qualifier


Normally, the last bit of a variable serves as a sign bit. value sign (+/-)





We can use all the bits to represent the value by declaring a variable as unsigned. To declare a variable as unsigned we add the ‘unsigned’ keyword before its type. unsigned int;  unsigned char; 

Unsigned Range


char (256 different values)  signed  unsigned




-127..+128 0..+255

int (4294967296 different values)  signed  unsigned

-2147483648.. +2147483647 0.. +4294967295

Unsigned - output


When using printf We use %d for signed variables and %u for unsigned ones void main() { unsigned char u = 200; char s; printf("%d\n", u); printf("%u\n", u);

200

s = u;

-56 printf("%d\n", s); printf("%u\n", s); }

4294967240

Overflow






Happens when a variable gets assigned a value that is outside of its range This is equivalent to saying that the number of bits required to encode the value exceeds the number of bits in the variable The value of the variable will usually be corrupted

Overflow Example #include <stdio.h> void main() { int iA = 1000, iB = 1000000, iC = 3000000, iD = 5000000; printf ("%d * %d = printf ("%d * %d = printf ("%d * %d = printf ("%d * %d = }

%d\n", %d\n", %u\n", %u\n",

iA, iA, iA, iA,

iB, iC, iC, iD,

iA*iB); iA*iC); iA*iC); iA*iD);

1000000000 -1294967296 3000000000 705032704

Casting







Sometimes it is desirable for a variable of one type to be considered as belonging to another in an operation We say the variable is cast to the new type. The casting operator is of the form: (type) For example, (float)i casts the variable i to a float.

IO functions from <stdio.h>  printf

- prints formatted output to stdout  scanf - reads formatted input from stdin  puts - prints a string to stdout  gets - reads a string from stdin  putc - prints a character to stdout  getc, getchar - reads a character from stdin

Operators
Types       

of operators in C:

Arithmetic Operators Increment and Decrement Operators Relational Operators Logical Operators Modulo Operator Assignment Operator Shortcut Operators

Arithmetic Operators Arithmetic Function Operator + Used for Addition

-

Used for Subtraction

*

Used for Multiplication

/

Used for Division

Examples 5 + 2 is 7 (int) 5.0 + 2.0 is 7.0 (float) 5 – 2 is 3 5.0 – 2.0 is 3.0 5 * 2 is 10 5.0 * 2.0 is 10.0 5.0 / 2.0 is 2.5 (float) 5 / 2 is 2 (int)

Increment and Decrement Operators Operator

Function

Examples

++

Increment operator adds 1 to its operand

int x = 10; x++; /*equal to 11*/

--

Decrement operator subtracts 1 to its operand

int x = 10; x--; /*equal to 9*/

Increment and Decrement Operators
++

and -- may be used either as prefix operators (before the variable) or as postfix operators (after the variable).

Increment and Decrement Operators
Example:

int num1 = 5; int num2 = 0; num1++; --num2; num2 = num1++; num2 = ++num1;

/*num1 == 6*/ /*num2 == -1*/ /*num2 is assigned value 6 *and num1 incremented*/ /*num1 incremented and *num2 is assigned value of ? */

Exercise 3 Write a program in C that asks the user to input the radius of a circle in centimeters (or portions of centimeters), and then output the area and the circumference of the circle to the screen. The formula for the area is A = πr² and the formula for the circumference is C = 2πr, where r is the radius and π can be approximated to be 3.1416.

Exercise 4 Write a program in C that asks the user to input two integers, one at a time, and then outputs the sum and product to the screen.

Relational Operators


The result of a statement using relational operators could either be 0 (false) and nonzero values (true). Relational Operator < > <= >= == !=

Function

less than greater than less than or equal to greater than or equal to equal to not equal to

Relational Operators
Examples: char ch1 = 'c';

int number1 = 10; int number2 = 3; ch1 == 'f' 7 != number1 number2 > number1 number2 < number1

/*false*/ /*true*/ /*false*/ /*true*/

Logical Operators
The

result of a statement using logical operators could either be 0 (false) and non-zero values (true).
Logical operators    

Logical Logical Logical Logical

AND OR NOT XOR

&& || ! ^

Logical Operators



Logical AND Form: op1 && op2 op1

op2

result

nonzero nonzero 0 0

nonzero 0 nonzero 0

nonzero 0 0 0

Logical Operators



Logical OR Form: op1 || op2 op1

op2

result

nonzero nonzero

nonzero

nonzero 0

nonzero

0

nonzero

nonzero

0

0

0

Logical Operators



Logical NOT Form: !op1 op1 result nonzero 0 0 nonzero

Logical Operators



Logical XOR Form: op1 ^ op2 op1

op2

result

nonzero nonzero

0

nonzero 0

nonzero

0

nonzero

nonzero

0

0

0

Logical Operators
Examples:

int B1 = 1; int B2 = 0;

/*true*/ /*false*/

B1 && B2; B1 || B2; !B1; B1 ^ B2 ;

/*false*/ /*true*/ /*true*/ /*true*/

Modulo Operator (%)






C allows us to perform modulo operations using the % symbol. This means that if, for example, x and y are two integer variables, the operation x % y will return the remainder of the operation (dividing the first operand by the second). Examples: 10% 3 2 % 3

(this is equal to 1) (this is equal to 2)

Assignment Operator
An

assignment Operator stores a value or a computational result in a variable. It is used to perform most arithmetic operations in a program.


The

syntax is:

= <expression>;

Shortcut Operators
Any

statement of the form:

= <expression>;

where operator is one of the binary operators + - * / % can be written in the form: =<expression>;

Shortcut Operators
Examples:

a c d e f

= = = = =

a c d e f

+ – * / %

b 4 5 3 2

can can can can can

be be be be be

written written written written written

as as as as as

a c d e f

+= -= *= /= %=

b 4 5 3 2

Operator Precedence ! * / % + < <= > >= == != ^ && || = += -= *=

/= %=

(right-associative) (left-associative) (left-associative) (left-associative) (left-associative) (left-associative) (left-associative) (left-associative) (right-associative)

Lesson Review Precompiler directives or preprocessors are statements in C that are processed before compilation.
A library is a collection of useful functions and symbols that may be accessed by a program
Declarations:Type declarations, Variable/constant declarations, Function/procedure declarations and Main function declarations


Lesson Review





C Statements are lines of code ending with a semicolon (;). Blocks are groups of statements enclosed in curly braces {}. C has at least 3 basic data types: Character (char), Integer (int) and Floating point (float). You can define your own data types by using typedef. Type declaration using basic data types has the following syntax: typedef ;

Lesson Review








You can declare your own constants in C by using const or #define. The syntax for const is: const = ; The syntax for #define is: #define [value] A variable in C is declared using the following syntax: [= ];

Lesson Review We use printf function to print to the screen and scanf to get input from the keyboard.
The types of operators in C are: Arithmetic Operators, Increment and Decrement Operators, Relational Operators, Logical Operators, Modulo Operator, Assignment Operator and Shortcut Operators. They follow a certain precedence.


Exercise 5
Write

a program that receives three integers as input and outputs the numbers in increasing order.

Control Structures Lesson 4

Control Structures
Kinds  

Sequence Control Structures Selection Control Structures






of Control Structures

if if-else switch

Repetition Control Structures




while do-while for

Sequential Program int main() { statement1; statement2; …. statementN; }

statement1

statement2

statementN

if Statement


used to conditionally execute a statement or block of statement.

if (expression) statement;

True or False





In C, every expression has a numeric value An expression is ‘true’ when its value is nonzero it is false it evaluates to zero. Therefore, in the following – if (expression) statement statement is executed if expression evaluates to non-zero.

if-else Statement if (expression) statement1; else statement2;








if expression is false, statement2 is executed both statements can be (and very often are) replaced by blocks of statements (“compound statements”) The else portion is optional.

Multiple if-else constructs


Multiple if-else constructs can also be used to choose between three of more options. TRUE

if (expression1) statement1; else if (expression2) statement2; else statement3;

expression1

statement1

FALSE expression2 FALSE statement3

rest of program

TRUE

statement2

The conditional or ternary operator: ‘?: ‘


The ?: operator is a more efficient form for expressing simple if statements.




It has the following form: <expression1>? <expression2>: <expression3>




It simply states: if (<expression1>) <expression2>; else <expression3>;

The conditional or ternary operator: ‘?: ‘


Example: 

Suppose we want to assign the maximum of a and b to z. Using the ? operator, we have the following statement: z = (a > b) ? a : b;




which is the same as: if (a > b)

z = a; else

z = b;

switch Statement


A multi-way conditional statement  similar to the if … else if … else …  allows the selection of an arbitrary number of choices based on an integer value switch (<expression>) { case : <statements> case : <statements> …. …. case : <statements> default : <statements> }

switch Statement


expression must have an integer value (char, int)




when the switch statement is executed:  the expression is evaluated  if a case matches the value of the expression, the program jumps to the first statement after that case label  otherwise, the default case is selected  the default is optional

while loop
The while loop has the following while ()

syntax:

<statement> 

where,





The boolean_expression in the syntax can be any expression that evaluates to TRUE or FALSE only. The statement can be either a simple statement or a compound statement.

while loop FALSE expression 



The statement is executed as long as condition is true. The loop terminates when the condition is no longer true.

TRUE statement/s

rest of program

while loop
Here

is a simple example of the use of the while loop: i=1 while (i<=5) { printf("%d",i); i++; }

while loop
There

are some things you have to remember when using the while loop. First

and foremost is that the while loop must terminate eventually. This means that you have to make sure that the boolean expression must evaluate to FALSE at some foreseeable point. Loops that do not terminate are called infinite loops.

do-while loop statement/s TRUE

do { statement(s); } while ( condition );

condition FALSE rest of program

Similar to while loops Except the condition is evaluated after the loop body The loop body is always executed at least once, even if the expression is never true 

do-while loop
Example:

i=1; do { printf("%d", i); i++; } while (i<=5);

for loop initialization

for ( ; ; ) { statement(s); }

condition

statement(s)

increment

rest of program

break and continue
C

provides two commands to control how we loop:  

break – to exit from a loop or a switch continue – skip an iteration of the loop

End