convert unsigned int to char alphabets - c

Question

I have the following code that converts a stream data of 16-bit integer to unsigned 8-bit integer.
I am looking to convert them to alphabetical data values and see what they contain.
#include<stdio.h>
int main() {
FILE *fp,*out;
char buffer[256];
size_t i = 0;
fp=fopen("c:/Gosam/input.txt", "rb");
if(fp != NULL) {
fread(buffer, sizeof buffer,1, fp);
}
out = fopen("c:/Gosam/res.txt", "w");
if(out != NULL) {
// buffer = (char*) malloc (sizeof(char)*Size);
for( i = 0; i < sizeof(buffer); i += 2)
{
const unsigned int var = buffer[i] + 256 * buffer[i + 1];
fprintf(out, "%u\n", var);
}
fclose(out);
}
fclose(fp);
}
The following is the form of my output:
263 4294966987 4294967222 4294967032 64 4294967013 73 4294967004 90
4294967028 83 4294966975 37 4294966961 5 4294966976 82 4294966942
4294967022 4294966994 11 4294967024 29 4294966985 4294966986 4294966954 50
4294966993 4294966974 4294967019 4294967007
This are the values I want to convert to alphabetical characters and see their content.

Answer 1

I don't know what you expect as an answer (you didn't ask a question), but there seems to be one suspicious thing in your code:
char buffer[256];
Here char means signed char. If your code does manipulations on them (like multiplying by 256), it probably doesn't do what you expect (though I can only guess what you expect - your question doesn't mention it).
Try the following:
unsigned char buffer[256];
Also please ask a question (that is, something with a question mark), and give some examples (input, output).

Answer 2

Your basic mistakes were:
after opening the inputfile checking out instead of fp against NULL
fread until eof won't return the number of characters that could be read (I've used fseek and ftell for this purpose)
writing uint values instead of char values to your file
I've fixed them and commented the affected lines appropriate. I also changed the buffer to use dynamic memory allocation instead of static allocation (that's how you can allocate memory for a buffer of a size that is unknown at compile-time). Please try the following code, which will copy all ASCII characters from one file to your output file (which is probably what you meant by 'alphabetical strings'):
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[]){
FILE *fp, *out;
char *buffer = NULL; /* use a pointer for dynamic memory allocation */
size_t i = 0, charCount = 0;
fp = fopen("c:/input.txt", "r"); /*read as ascii - not binary */
if(fp != NULL){ /*use 'fp' here 'out' is not initalized */
fseek(fp, 0, SEEK_END); /* go to end of the file */
charCount = ftell(fp) - 1; /* get position */
fseek(fp, 0, SEEK_SET); /* return to the beginning of the file */
buffer = (char*)malloc(sizeof(char)*charCount); /* allocate memory */
fread(buffer, sizeof(char) * charCount, 1, fp); /* reads all characters from the file */
}
out = fopen("c:/output.txt", "w");
if(out != NULL){
for(i = 0; i < charCount; i += 1){ /* loop from 0 to count of characters */
const unsigned char var = buffer[i];
fprintf(out, "%c", var);
}
fclose(out);
}
fclose(fp);
if(buffer != NULL){
free(buffer); /* deallocate memory */
}
return 0;
}