#include<stdio.h>
#define MAX 30
struct stack
{
	int data[MAX];
	int top;
};
void inits(struct stack * s)
{
	s->top= -1;
	
}
void push(struct stack * s,int num)
{
	s->data[++s->top] = num;
}
int pop(struct stack * s)
{
	return(s->data[s->top--]);
}
void evaluate(struct stack *s,char op,int num1,int num2)
{
	int ans;
	switch(op)
	{
		case '+' : ans=num1+num2;
					break;
		case '-' : ans=num1+num2;
					break;
		case '*' : ans=num1+num2;
					break;
		case '/' : ans=num1+num2;
					break;
		case '^' : 
		case '$' : ans=num1+num2;
					break;						
		}
		push(s,ans);
}
int gettype(char ch)
{
	switch(ch)
	{
		case '+' :
		case '-' :
		case '*' :
		case '/' :
		case '$' :
		case '^' : return 1;
		default: return 0;
	}
}
void main()
{
	char postfix[MAX];
	int num1, num2, element, i, ans;
	struct stack s;
	inits(&s);
	printf("\nEnter postfix expression");
	scanf("%s",postfix);
	for(i=0; postfix[i]!='\0';i++)
	{
		switch(gettype(postfix[i]))
		{
		case 0: push(&s,postfix[i]-'0');
				break;
		case 1: num2 = pop(&s);
				num1 = pop(&s);
				evaluate(&s, postfix[i],num1,num2);
		}
	}
printf("The answer of %s=%d", postfix,s.data[s.top]);
}
by

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Read inputs from stdin

OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.

#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

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
}