C program without using main function

Write a C program without using main function.
In this program, we didn’t use the main function, but we are using the preprocessor directive #define with arguments to define the Main function.
A Preprocessor is program which processes the source code before compilation.
The ‘##‘ operator is called the token pasting or token merging operator. In the second line of program we used it to merges the 4th,1st,3rd & the 2nd characters(tokens), and it compiles as “msut”.
When the controller calls int begin, preprocessor replaces the macro “begin” with the expansion decode(a,n,i,m,a,t,e). As defined in the macro decode it merges the 4th,1st,3rd & the 2nd characters, and int begin becomes int main(), so program runs successfully. Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.
–>

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***********************************************************/

#include<stdio.h>
#define decode(s,t,u,m,p,e,d) m##s##u##t
#define begin decode(a,n,i,m,a,t,e)

int begin()

{
printf(” Ha HA see how it is?? “);
}
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C Aptitude Questions and answers with explanation

C Aptitude 14
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 14.1

  main()
{
struct xx
{
int x;
struct yy
{
char s;
struct xx *p;
};
struct yy *q;
};
}


Answer: Compiler Error

Explanation: in the end of nested structure yy a member have to be declared

C aptitude 14.2

  main()
{
extern int i;
i=20;
printf("%d",sizeof(i));
}

Answer: Linker error: undefined symbol ‘i’.

Explanation:extern declaration specifies that the variable i is defined somewhere else. The compiler passes the external variable to be resolved by the linker. So compiler doesn’t find an error. During linking the linker searches for the definition of i. Since it is not found the linker flags an error.

C aptitude 14.3

     main()
{
printf("%d", out);
}

int out=100;

Answer: Compiler error: undefined symbol out in function main.

Explanation: The rule is that a variable is available for use from the point of declaration. Even though a is a global variable, it is not available for main.

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C Aptitude Questions and answers with explanation

C Aptitude 7
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 7.1

  main()
{
printf("nab");
printf("bsi");
printf("rha");
}

Answer: hai

Explanation: n – newline b – backspace r – linefeed

C aptitude 7.2

  main()
{
int i=5;
printf("%d%d%d%d%d%d",i++,i--,++i,--i,i);
}

Answer:45545

Explanation:The arguments in a function call are pushed into the stack from left to right. The evaluation is by popping out from the stack. and the evaluation is from right to left, hence the result.

C aptitude 7.3

    #define square(x) x*x
main()
{
int i;
i = 64/square(4);
printf("%d",i);
}

Answer:64

Explanation: the macro call square(4) will substituted by 4*4 so the expression becomes i = 64/4*4 . Since / and * has equal priority the expression will be evaluated as (64/4)*4 i.e. 16*4 = 64

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C Aptitude Questions and answers with explanation.

C Aptitude 3
C program is one of most popular programming language which used for core level of coding across the board. Now a days C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program. Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 3.1

   main()
{
int i=-1,j=-1,k=0,l=2,m;
m=i++&&j++&&k++||l++;
printf("%d %d %d %d %d",i,j,k,l,m);
}

Answer: 0 0 1 3 1

Explanation:Logical operations always give a result of 1 or 0 . And also the logical AND (&&) operator has higher priority over the logical OR (||) operator. So the expression ‘i++ && j++ && k++’ is executed first. The result of this expression is 0 (-1 && -1 && 0 = 0). Now the expression is 0 || 2 which evaluates to 1 (because OR operator always gives 1 except for ‘0 || 0’ combination- for which it gives 0). So the value of m is 1. The values of other variables are also incremented by 1.

C aptitude 3.2

main()
{
char *p;
printf("%d %d ",sizeof(*p),sizeof(p));
}


Answer:12

Explanation:The sizeof() operator gives the number of bytes taken by its operand. P is a character pointer, which needs one byte for storing its value (a character). Hence sizeof(*p) gives a value of 1. Since it needs two bytes to store the address of the character pointer sizeof(p) gives 2.

C aptitude 3.3

  main()
{
int i=3;
switch(i)
{
default:printf("zero");
case 1: printf("one");
break;
case 2:printf("two");
break;
case 3: printf("three");
break;
}
}



Answer:three

Explanation: The default case can be placed anywhere inside the loop. It is executed only when all other cases doesn’t match.

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C Aptitude Questions and answers with explanation.

C Aptitude 2
C program is one of most popular programming language which used for core level of coding across the board. Now a days C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program. Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 2.1

 main()
{
static int var = 5;
printf("%d ",var--);
if(var)
main();
}

Answer: 5 4 3 2 1

Explanation: When static storage class is given, it is initialized once. The change in the value of a static variable is retained even between the function calls. Main is also treated like any other ordinary function, which can be called recursively.

C aptitude 2.2

main()
{
int c[ ]={2.8,3.4,4,6.7,5};
int j,*p=c,*q=c;
for(j=0;j<5;j++) {
printf(" %d ",*c);
++q; }
for(j=0;j<5;j++){
printf(" %d ",*p);
++p; }
}



Answer: 2 2 2 2 2 2 3 4 6 5

Explanation:Initially pointer c is assigned to both p and q. In the first loop, since only q is incremented and not c , the value 2 will be printed 5 times. In second loop p itself is incremented. So the values 2 3 4 6 5 will be printed.

C aptitude 2.3

 main()
{
extern int i;
i=20;
printf("%d",i);
}


Answer:Linker Error : Undefined symbol ‘i’

Explanation: extern storage class in the following declaration, extern int i; specifies to the compiler that the memory for i is allocated in some other program and that address will be given to the current program at the time of linking. But linker finds that no other variable of name i is available in any other program with memory space allocated for it. Hence a linker error has occurred .

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C Aptitude Questions and answers with explanation.

C Aptitude 1
C program aptitude questions, answers and explanation for interview preparations.
In this site, We discussed various type of C programs, now we are moving into further steps by looking at the c aptitude questions.
This questions and answers are helpful to freshers and job hunters. C interview questions are from various companies and experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.
Predict the output or error(s) for the following:

C aptitude 1.1

void main()
{
int const * p=5;
printf("%d",++(*p));
}

Answer: Compiler error: Cannot modify a constant value.

Explanation: p is a pointer to a “constant integer”. But we tried to change the value of the “constant integer”.

C aptitude 1.2

main()
{
char s[ ]="man";
int i;
for(i=0;s[ i ];i++)
printf("n%c%c%c%c",s[ i ],*(s+i),*(i+s),i[s]);
}


Answer: mmmm aaaa nnnn

Explanation: s[i], *(i+s), *(s+i), i[s] are all different ways of expressing the same idea. Generally array name is the base address for that array. Here s is the base address. i is the index number/displacement from the base address. So, indirecting it with * is same as s[i]. i[s] may be surprising. But in the case of C it is same as s[i].

C aptitude 1.3

 main()
{
float me = 1.1;
double you = 1.1;
if(me==you)
printf("I love U");
else
printf("I hate U");
}


Answer: I hate U

Explanation: For floating point numbers (float, double, long double) the values cannot be predicted exactly. Depending on the number of bytes, the precession with of the value represented varies. Float takes 4 bytes and long double takes 10 bytes. So float stores 0.9 with less precision than long double. Rule of Thumb: Never compare or at-least be cautious when using floating point numbers with relational operators (== , >, <, <=, >=,!= ) .

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K & R C Programs Exercise 5-14.

K and R C, Solution to Exercise 5-14:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write a C program to handle a -r flag which indicates sorting in reverse (decreasing) order. But sure that -r works with -n.Read more about C Programming Language .

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* programs for commercial purposes,
* contact info@c-program-example.com
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* and browse!
*
* Happy Coding
***********************************************************/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define TRUE 1
#define FALSE 0

#define MAXLINES 5000
char *lineptr[MAXLINES];

#define MAXLEN 1000

int reverse = FALSE;

int getline(char s[], int lim)
{
int c, i;

for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != 'n'; i++)
s[i] = c;
if (c == 'n') {
s[i++] = c;
}
s[i] = '';
return i;
}


int readlines(char *lineptr[], int maxlines)
{
int len, nlines;
char *p, line[MAXLEN];

nlines = 0;
while ((len = getline(line, MAXLEN)) > 0)
if (nlines >= maxlines || (p = malloc(len)) == NULL)
return -1;
else {
line[len - 1] = '';
strcpy(p, line);
lineptr[nlines++] = p;
}
return nlines;
}


void writelines(char *lineptr[], int nlines)
{
int i;

for (i = 0; i < nlines; i++)
printf("%sn", lineptr[i]);
}

int pstrcmp(const void *p1, const void *p2)
{
char * const *s1 = reverse ? p2 : p1;
char * const *s2 = reverse ? p1 : p2;

return strcmp(*s1, *s2);
}

int numcmp(const void *p1, const void *p2)
{
char * const *s1 = reverse ? p2 : p1;
char * const *s2 = reverse ? p1 : p2;
double v1, v2;

v1 = atof(*s1);
v2 = atof(*s2);
if (v1 < v2)
return -1;
else if (v1 > v2)
return 1;
else
return 0;
}

int main(int argc, char *argv[])
{
int nlines;
int numeric = FALSE;
int i;

for (i = 1; i < argc; i++) {
if (*argv[i] == '-') {
switch (*(argv[i] + 1)) {
case 'n': numeric = TRUE; break;
case 'r': reverse = TRUE; break;
default:
fprintf(stderr, "invalid switch '%s'n", argv[i]);
return EXIT_FAILURE;
}
}
}

if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
qsort(lineptr, nlines, sizeof(*lineptr), numeric ? numcmp : pstrcmp);
writelines(lineptr, nlines);
return EXIT_SUCCESS;
} else {
fputs("input too big to sortn", stderr);
return EXIT_FAILURE;
}
}


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K & R C Programs Exercise 3-2.

K and R C, Solution to Exercise 3-2:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
C Program that converts the characters like newline and tab into visible escape sequences like n and t as it copies the string t to s. Use a Switch case, and Write the function for the other direction as well, converting escape sequences into the real characters. Read more about C Programming Language .

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*
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***********************************************************/

#include <stdio.h>

void escape(char * s, char * t);
void unescape(char * s, char * t);

int main(void) {
char text1[50] = "aHello,ntWorld! Mistakeeb was "Extra 'e'"!n";
char text2[51];

printf("Original string:n%sn", text1);

escape(text2, text1);
printf("Escaped string:n%sn", text2);

unescape(text1, text2);
printf("Unescaped string:n%sn", text1);

return 0;
}

/*escape: expand newline and tab and others tabs into visible sequences using switch*/

void escape(char * s, char * t) {
int i, j;
i = j = 0;

while ( t[i] ) {



switch( t[i] ) {
case 'n':
s[j++] = '\';
s[j] = 'n';
break;

case 't':
s[j++] = '\';
s[j] = 't';
break;

case 'a':
s[j++] = '\';
s[j] = 'a';
break;

case 'b':
s[j++] = '\';
s[j] = 'b';
break;

case 'f':
s[j++] = '\';
s[j] = 'f';
break;

case 'r':
s[j++] = '\';
s[j] = 'r';
break;

case 'v':
s[j++] = '\';
s[j] = 'v';
break;

case '\':
s[j++] = '\';
s[j] = '\';
break;

case '"':
s[j++] = '\';
s[j] = '"';
break;

default:



s[j] = t[i];
break;
}
++i;
++j;
}
s[j] = t[i];
}


/* unescape: convert escape sequences into real charecters while copying the string t to s */

void unescape(char * s, char * t) {
int i, j;
i = j = 0;

while ( t[i] ) {
switch ( t[i] ) {
case '\':


switch( t[++i] ) {
case 'n':
s[j] = 'n';
break;

case 't':
s[j] = 't';
break;

case 'a':
s[j] = 'a';
break;

case 'b':
s[j] = 'b';
break;

case 'f':
s[j] = 'f';
break;

case 'r':
s[j] = 'r';
break;

case 'v':
s[j] = 'v';
break;

case '\':
s[j] = '\';
break;

case '"':
s[j] = '"';
break;

default:



s[j++] = '\';
s[j] = t[i];
}
break;

default:



s[j] = t[i];
}
++i;
++j;
}
s[j] = t[i];
}


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K&R C Program Exercise 1-02

K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language, second addition, by Brian W.Keringhan and Dennis M.Ritchie(Prentice Hall,1988). You can learn and solve K&R C Programs Exercise. Experiment to find what happens when printf’s argument string contains c, where c is some character not listed above. Read more about C Programming Language .

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/*Exercise 1-02:.*/

#include<stdio.h>

main()
{
printf("hello, worlda");
printf("hello, world7");
printf("hello, world?");
}


/*Output: The result of this experiment is compiler dependent. One possible result might be:
hello, world hello, worldhello, world?
where is a short beep produced by ASCII*/
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K&R C Program Exercise 1-01(b)

K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language, second addition, by Brian W.Keringhan and Dennis M.Ritchie(Prentice Hall,1988). You can learn and solve K&R C Programs Exercise. Run the “hello, world” program on your system. Experiment with leaving out parts of the program to see what error messages you get. Read more about C Programming Language .


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* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/



#include<stdio.h>

main()
{
printf("hello, worln")
}


/*Output: The semicolon (;) is missing after printf(). The compiler should recognize that the semicolon is missing and print the appropriate message:
1-1b.c: In function 'main':
1-1b.c:8:1: error: expected ';' before '}' token*/
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