Engineering Clinic

Like numbered arrays, C handles character arrays (strings).
Each string is identified as a character array and ends with a ‘\0’(null) character (the compiler automatically adds the null character). So the end of string is identified as a null character. Being an array, all the elements of the string array stored in continuous memory locationsfollowing is the declaration of character array
char name[50];
or
char name[]=”Pradeep Kumar”;
or
char name[20]=”Hello Pradeep”; Strings can be handled or manipulated through loops or library functions. There are some library functions to handle strings are available at string.h
Some of them are
strlen(string)
This is to find the length of the string and returns an integer For example, if “Hello” is the string, the length will be 5 and “Hello “, the length is 6 (there is a blank space after o in hello)strcat(String1, string2)
to concatenate two strings One string will be appended to another string (the concatenation happens by inserting t…

Arrays in C programming starts with memory addresses. Yes the compiler handles arrays as memory addresses.
Similar elements group together with a single name is called arraythe indexing always starts with 0 and ends at n-1 (if the size of the array is n)Array elements stores in consecutive memory location. The array elements usually stores in consecutive memory location. For example,
int a[10];  //Array with size 10 the above example is an integer array with size 10 or this array can hold 10 variables.
The elements starts from a[0], a[1], a[2]…..a[9], so totally there are 10 elements.
Array elementsvaluesmemory address locationa[0]32600AH  (This address is called as the base address)a[1]34600EHa[2]236012Ha[3]356016Ha[4]45601AHa[5]67601EHa[6]566022Ha[7]16026Ha[8]34602AHa[9]25602EH The memory addresses shown above are in hexadecimal, that’s why each address suffixed with a letter H. The memory addresses in each machine will be different.
The base address is the address where the first e…

Almost all the programming languages uses functions. Functions are the entities which are grouping a set of statements which do a specific job or set of jobs.
Example: sum of integers, sum of float number, complex number addition.
All the above three can be implemented as a single function or three separate functions.
When someone wants to use that, a function can be simply called.
So function implementation happens as
Function prototype or Function declarationFunction definition or function implementationFunction callFunction prototype
It is necessary to specify the name of the function, the parameters and the return type to the compiler that the function is being defined in this program.The prototype ends with a semicolon syntax:
int sum(int, int); //function prototypeFunction Definition
This is the actual function definition which shows the function implementation.
for the above syntax here is the function
int sum(int a, int b)
{
int c;
c=a+b;
return c;
} The above function is …

C supports Decision Making and Looping (Interations)
In decision Making,
if, if-else, if- else if – else, switch – case is used.
if(condition)
{
//These statements are executed only if the condition is true or 1
} if – else
if(condition)
{
//These statements are executed only if the condition is true or 1
}
else
{
//these statement are executed only if the condition is false or 0
}
(in the above example, there is no else part means that for some situation, there may not be a need for else part) if – else if – else
if(condition 1)
{
//These statements are executed if the condition 1 is true or 1
}
else if (condition 2)
{
//These statements are executed if the condition 2 is true or 1
}
else
{
//These statements are executed neither condition 1 nor condition 2 are true
// if all the conditions fails, then this statement will execute
} Switch Case
switch (expression)
{
case 1: statement 1;
break;
case 2: statement 2;
break;
case 3: statement 3;
break;
default: statement d;
break;
}
…

Declaration of variable names does two things
it tells the compiler what the variable name is specifies what type of data the variable will hold So it is mandatory that each variable should belong to a particular data type. C supports different data types like integer, character, float, double, etc.
Data type Size on a 16 bit machineRangechar1 byte or 8 bits-128 to 127signed char1 byte-128 to 127unsigned char1 byte0 to 255short int or short1 byte-128 to 127int2 bytes-32768 to 32767unsigned int2 bytes0 to 65535long int or long4 bytes-2,147,483,648 to 2,147,483,647unsigned long int4 bytes0 to 4,294,967,295float4 bytes3.4E-38 to 3.4 E+38double8 bytes1.7E-308 to 1.7E+308long double10 bytes3.4E-4932 to 1.1E+4932 Example of declaring variables
int a=20,b=20,c;
int a=10;
int b=9;
int c=20;
float c=3.5;
char a =’A’;
long int al or long a;
short int b or short b;
double c;
long double c;
 T S Pradeep Kumar

Tokens are classified as
KeywordsIdentifiersOperatorsConstantsSpecial SymbolsKeywords
Keywords are reserved by the compilers and keywords will not be redefined (means the keywords are not been declared as variable names, etc). There are standard 32 keywords in C compiler, and some compilers uses more keywords based on their specification. Here is the list of 32 keywords
autobreakcasecharconstcontinuedefaultdodoubleelseenumexternfloatforgotoifintlongregisterreturnshortsignedsizeofstaticstructswitchtypedefunionunsignedvoidvolatilewhile
Identifiers
Identifiers are variable names declared inside the program. They use alphabets, number, symbols like _ and $They must begin with  alphabet or _ They are case sensitive i.e Var_name is different from var_nameSome valid identifiers are
johnValuer_siex1x2ChennaiSum1abcdinvalid identifiers
123%(super)25th1stab-dsum of total
Operators
operators are further classified into different categories like
Arithmetic operators +  - for addition   1+3 = 4
-  …

Printf() is a function to print strings to the display unit and
scanf() is to scan the input through the keyboard
the f in the printf and scanf are called as format. That is, printf() and scanf() will print and scan in some particular format, it is the duty of the developer to provide that formats.
For example
printf(“a=%d, b=%d”, a,b); //This function will print a=10, b=20 if the values of a and b are 10 and 20
scanf(“%f”, &a); //this will accept a float number as the specifier is %f which is for float, See the Ampersand symbol which to tell the compiler to store the variable into the address. Here is the list of format codes or format specifiers
scanf() format codes
CodeMeaning%cread a single character%dread a decimal integer%fread a floating point value%eread a floating point value (even in exponential format)%gread a floating point value%hread a decimal, heaxadecimal or octal integer%oread an octal integer%sread a string%uread an unsigned integer%xread a hexadecimal intege…

/* This program is written by T S Pradeep Kumar on 28th Sep 2010
This is to display Hello World to the display unit
*/
#include <stdio.h> //including the standard IO functions like printf(), scanf()
int main()
{
printf(“Hello World \n”);
return 0;
}stdio.h is the library which contains the printf(), scanf() and other standard IO functions, so before we use any function we need to include in our C program. Most of the compilers will take stdio.h automatically, even if we dont include in our programint main() {} is the main functionprintf(“Hello World\n”); printf() is the function which is printing to the display unit and it is displaying Hello World. Whatever is there inside the double quotes will displayed as it is in the monitor except the format specifiers or format codes (%d, %f, %c)return 0; is the final statement which returns the integer value 0 (this is just to make the compiler happy) Here in the above program, you can see there are semi colons ;
Every C stateme…

This post and the subsequent posts will help you in understanding the intricacies of C programming. These posts just shows you the basics of C programming and some worked examples for that. 

Features of C Programming
C is a small language having lesser number of keywords than Java or pascal.C is a native language of Unix, Linux. Not only that many of the windows packages, database programs, graphics libraries are written in C programC is portable – it provides standard set of libraries that work on the same way with all machinesC is modular, as it supports functions to divide the program in to sub program C is efficient on most machines, because certain constructs are machine dependant. Structure of a C program
Comments the comments are usually ignored by the compilerso this part informs about the author of the programwhat is the usefulness of this programupdation or creation of the programExample: //  - Single line comment/* ----- multi line comments    ….*/Preprocessor Directives bef…

This post has no relation with networks, however these C programs help anyone who started learning C programming. It covers from basics of C to Arrays and Functions.
The readers are requested to get their outputs, as the output screenshots were lost. Also most of these programs were solved by my student friends. If you encounter any errors in the programs, kindly comment below to get it rectified through other readers.

To compile these programs in
Windows : Use Dev-C++ for compilation (It GUI Based), Also you may remove #include <conio.h> if you encounter any error during compilation

In Linux: 
You may try the gcc or g++ compiler
Delete the #include <conio.h>
delete the line that contains getch(); 
Here is the command 
$] gcc -o first file.c 
$] ./first
(The file.c is compiled and linked to the binary file first and the output is executing in the second line using ./first)
See the following screenshot for the Question 1.

Question 1 
The straight line method of computing the yearl…