#include <stdio.h>
#include <ctype.h>

void main ()
{
char linearray s[ 100 ]; /* create char array */

printf( ''Enter a  line of text:\n'' );

/* use gets to read line of text*/
gets ( linearray s);

printf( ''%s%c\n, ''The line converted to uppercase is  '', toupper( ' line ');

printf( ''%s%c\n, '' The line converted to lowercase is '', tolower ('line');

return 0; /* indicates successful termination */

#include <stdio.h>
#include <ctype.h>

void main () comment: C standards indicate that retun type of the main function should be of type int
{
char linearray s[ 100 ]; /* create char array */ comment: you have whitespace in the variable name - not allowed. Is the variable name linearray or s?

printf( ''Enter a line of text:\n'' );

/* use gets to read line of text*/
gets ( linearray s); comment:  same problem as above, one variable name or the other.

printf( ''%s%c\n, ''The line converted to uppercase is '', toupper( ' line ');
comment: The brackets for the printf() function are not closed. the toupper function takes a single char, not an entire string, you will have to iterate through it, finally you have no variable named line, and if one did, it should not be encased in quotes.

printf( ''%s%c\n, '' The line converted to lowercase is '', tolower ('line');
comment: The brackets for the printf() function are not closed. the toupper function takes a single char, not an entire string, you will have to iterate through it, finally you have no variable named line, and if one did, it should not be encased in quotes.

return 0; /* indicates successful termination */
comment: you have not provided a closing brace for the main function

#include <stdio.h>
#include <ctype.h>

int main void
{
char array s[ 100 ]; /* create char array */

printf( ''Enter a  line of text:\n'' );

/* use gets to read line of text*/
gets ( array s);

printf( ''%s%c\n, ''The line converted to uppercase is  '', toupper );

printf( ''%s%c\n, '' The line converted to lowercase is '', tolower );

return 0; /* indicates successful termination */

} /* end main */

#include <stdio.h>
#include <ctype.h>

int main void
{
char array s[ 100 ]; /* create char array */ comment:  again, you have tow variable names, it will need to look like the following: char s[100];

printf( ''Enter a line of text:\n'' );

/* use gets to read line of text*/
gets ( array s); comment: same as above, will need to resemble gets(s);

printf( ''%s%c\n, ''The line converted to uppercase is '', toupper ); comment: toupper is a function that takes a single char as a parameter, you will need to use a looping mechanism to talk through each element of the array and apply the function to each element.

printf( ''%s%c\n, '' The line converted to lowercase is '', tolower );
comment: lower is a function that takes a single char as a parameter, you will need to use a looping mechanism to talk through each element of the array and apply the function to each element.

return 0; /* indicates successful termination */

} /* end main */

int main(int argc, char *argv[])
{
  char str1[256];
  int i;
  printf("Please enter a string:\n");
  gets(str1);
  for(i=0;i<strlen(str1);i++)
     str1[i]=toupper(str1[i]);
  printf("The upper string is: %s\n",str1);
  for(i=0;i<strlen(str1);i++)
     str1[i]=tolower(str1[i]);
  printf("The lower string is: %s\n",str1);
  return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(int argc, char *argv[])
{
  char s[100];
  int i;
  printf("Please enter a string:\n");
  gets(s);
  for(i=0;i<strlen(s);i++)
     s[i]=toupper(s[i]);
  printf("The upper string is: %s\n",s);
  for(i=0;i<strlen(s);i++)
     s[i]=tolower(s[i]);
  printf("The lower string is: %s\n",s);
  return 0;
}