C BASICS

Content

C Lang Intro

Flow Control

Loops

Arrays

Example: Bubble sort

Example: Sieve of Eratosthenes

C Lang Intro

Flexible & compact lang
From operating systems to games
Basis for more advanced langs
Lang defined by an international standard (C11)
Some elements in C11 optional
C11 also defines a standard library for C
- Common constants, symbols, functions, etc.
- Optional extensions to C lang
Machine-dependet facilities implemented in machine-independet form (e.g. I/O)
Standard library defined by a set of header files (.h)
App dev includes the according headers

Compiler & Linker

Compiler converts source code into machine lang
Detects and reports errors
Compiler outputs object code to object files (.obj, .o)
Compilation phases
- Preprocessing phase: source code may be modified or added
- Actual compilation
Linker
- Combines object files
- Adds required modules from std lib
- Links everything to an executable
- Also reports problems (reference errors)

C Development

Build with command line
1. Start - Visual Studio Tools
2. Developer Command Prompt - cd to dev folder
3. cl main.c (compiles and links main.c)
Create C++ Project in Visual Studio
1. File - New - Project
2. Visual C++ - Empty Project
3. Add a source file

First App

// main.c                        // This is a comment
#include <stdio.h>               // This is a preprocessor directive

int main()                       // Define function main
{                                // Mark beginning of main
    printf("Hi, there!\n");      // Print string to console
    return 0;                    // Return control to operating system
}                                // Mark end of main

Comments

// Comment 1: Compiler ignores everything with two slashes on a line

/* Comment 2 */

/* 
 * Comment 3:
 * Compiler ignores everything between /* ... */
 */

Preprocessing Directives

#include <stdio.h>         // # marks a preprocessing directive 

#define PI 3.1415          // define a constant

Preprocessing directive tells the compiler to do something before comping
Include header file into, define constants, etc...
Header file provides info about types and functions in the stdlib
Compiler uses info to integrate predefined functions or other objects to the app
E.g. info about printf(..)

Functions

int main()     // Function header 
{              // Opening brace
    // ...     // Function body
}              // Closing brace

Functions as named block of code that does something
Every C app needs at least the main function
Function signature
- defines return type
- defines function name
- defines input parameters with types
Keywords (reserved words) used to describe types (int, void, etc.)

Variables and Memory

App and data is stored in RAM
0/1 in memory
8 bit groups - byte
Each byte is labeled with a number (address)
1KB - 1024bytes
- 1023 = 2^10 = 11 1111 1111
Variables as piece of memory
- with one or more contiguous bytes
- 1, 2, 4 (32bit), 8, 16 bytes
- every variable has a name
Use variable name to store and retrieve data
Variable type specifies data size

Variables #2

Variable naming
- May contain upper/lowercase letters
- digits
- underscore
Must not begin with digit
Different type of variables store different type of data

#include <stdio.h>

int main(void)
{
    int salary;         // Declare a variable called salary
    salary = 10000;     // Store 10000 in salary
    printf("My salary is %d.\n", salary);
    return 0;
}

Variables #3

Variable declaration
- introduces a variable name
Variable definition
- causes memory to be allocated
Explicit/Implicit conversions
- compiler performs implicit conversions when no data loss
- explicit conversion needed if data loss possible

Flow Control

If Statement

if(a > b)
    printf('a is greater b');

if(a < b)
    printf('b is greater a');
else 
    printf('a is greater b');


if(a < b) 
{
    if(a < z) 
    {
        // ...
    }
    else 
    {
        // ...
    }
} 
else if(z < b) 
{
    // ...
}
else 
{
    // ...
}

Switch Statement

switch(customerId)
{
    case 35:
        printf('Customer id is 35');
        break;
    case 36:
        // ...
        break;
    default: 
        // ...
        break;
}

Loops

For Loop

for(int i = 0; i < 10; i++)
{
    // ...
}

int count = 0;
for( ; count < 10; ++count)
{
    // ...
}

for( ;; )
{
   // ...
   if(quitPrg)
        break;
}

i is defined once
loop expression is evaluated in each iteration
variable i is incremented in each iteration

While Loop

int i = 0;
int count = 10;
while(i < count)
{
   //...
   i++;
}

for( ;; ) 
{
    // ...
    while(true)
    {
       // ...
    }
    // ...
}

Arrays

#include <stdio.h>         // # marks a preprocessing directive

Preprocessing directive tells the compiler to do something before comping
Include header file into
Header file provides info about types and functions in the stdlib
Compiler uses info to integrate predefined functions or other objects to the app
E.g. info about printf(..)

References

Beginning C (5th Edition)

Ivor Horton

Thank you for your attention!