//Evaluate the postfix Expression
//Evaluate the postfix Expression
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<ctype.h>
#define MAX
int stack[MAX];
int top=-1;
void push(int e);
int pop();
void main(){
    char pe[30];//postfix expression
    int i,v,op1,op2;
    printf("Enter Postfix Expression:\n");
    gets(pe);
    for(i=0;pe[i]!='\0';i++){
        if(isalpha(pe[i])){
        printf("Enter value for %c",pe[i]);
        scanf("%d",&v);
        push(v);
        }
        else if(isdigit(pe[i]))
            push(pe[i]-'0');
        else{
            op2=pop();
            op1=pop();
            switch(pe[i]){
       case '+':
           push(op1+op2);
        break;
       case '-':
           push(op1-op2);
        break;
       case '*':
           push(op1*op2);
        break;
       case '/':
        push(op1/op2);
        break;
      // case '^':
       // push(pow(op1,op2));
       // break;
       case '%':
        push(op1%op2);
        break;
       default:
        printf("Invalid Case.\n");

            }
        }
    }
    printf("The result is %d:\n",stack[top]);
}
void push(int e){
    stack[++top]=e;
}
int pop(){

        return stack[top--];
}
by

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#include <stdio.h>
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About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}