Memory & arrays - Printing char array using printf

Ok , im printing two arrays of characters , one after another (with reading operations in between) first one comes out fine , but the second one comes out ending with the contents of first one. I suspect they are allocated consecutively in memory , and for some reason printing the second one also grabs the first one.
Here is the reading/printing part :

currentPointer=0;

//Skip over empty spaces
while(NumBuf[pointer] ==' ')
{
pointer++;
}

while(NumBuf[pointer] != ' ')
{
first[currentPointer]=NumBuf[pointer];
currentPointer++;
pointer++;
}
printf("Student First : %s \n",first);






//SECOND NAME!!!

currentPointer=0;

//Skip over empty spaces
while(NumBuf[pointer] ==' ')
pointer++;


while(NumBuf[pointer] !=',')
{
second[currentPointer]=NumBuf[pointer];
currentPointer++;
pointer++;
}
printf("\nStudent Second : %s \n",second);

}

And thats the output it gives:

15131227 Kelly Nesolon, 92 22 1 3 3
Student Num 15131227
Student First : Kelly
Student Second : NesolohВЪ©=Kelly

14151251 Jenny Craig, 91 31 1 1 3 3
Student Num 14151251
Student First : Jenny
Student Second : CraigohВЪ©=Jenny

First string is the input string , discard numbers after comma plz.
As you can see , Student Second gives weird output... Any idea??

A char[] is terminated by a null byte. That's how printf knows how to stop printing. If it's overwritten, then it will continue until it finds another null byte later on, and stops - after printing too much. I guess you know this much already.

Edit: I did have all the information I needed in the original post, I just didn't see it; I kinda just assumed it was done.


I need to know how everything (first,second,pointer,currentpointer, and any other such variables) is declared; including the order.

The clue is that something else is sharing memory space with second from [5] and out. I would guess that this space is probably written to as part of saving the current value of pointer and/or currentpointer (which has been kept in registers for the loop) before the call to printf. However, unless they are char (aka 8 bit int) in size that would also introduce null bytes. (They ARE index ints rather than pointers, right?)


For now, the only recommendation I can truly give is to use C++ rather than C - using high-level classes like the standard library string means it handles all of these gory little details for you and lets you concentrate on the overall program.

Oh , and yeah , as much as i want , i cannot use C++ , its a course in C.
Brutal low level C.


#include <stdio.h>

#include <stdlib.h>



int main()

{
//
FILE * pFile;
pFile = fopen ("file","r");



if (pFile==NULL)

printf("Error opening file: my.txt");

else

{

char studNum[8],first[10];
char second[10];
int final,midterm,quiz1,quiz2,quiz3;

double finalGrade;

char NumBuf [100];
int ch;

printf("Got here 1\n");

while((ch = (getc(pFile))) != EOF)
{
int lenght = 0;
while(ch!='\n' && ch!=EOF)
{

if(lenght <= 99)
{
NumBuf [lenght] = ch;
}
ch = (getc(pFile));
lenght++;


}

//If line is longer then 99 , omit it
if(lenght <= 99)
{
if(ch!=EOF)
printf("%s\n",NumBuf);

// BREAKING INTO SEPARATE STRINGS!!!

int pointer = 0;
int currentPointer = 0;

//STUDENT NUMBER!!!
while(NumBuf[pointer] != ' ')
{
if(isdigit(NumBuf[pointer]))
{
// printf("%i",pointer);
studNum[currentPointer]=NumBuf[pointer];
currentPointer++;
}
pointer++;

}
printf("Student Num %s \n",studNum);

//FIRST NAME!!!
currentPointer=0;

//Skip over empty spaces
while(NumBuf[pointer] ==' ')
{
pointer++;
}

while(NumBuf[pointer] != ' ')
{
first[currentPointer]=NumBuf[pointer];
currentPointer++;
pointer++;
}
printf("Student First : %s \n",first);





//SECOND NAME!!!
currentPointer=0;

//Skip over empty spaces
while(NumBuf[pointer] ==' ')
pointer++;

while(NumBuf[pointer] !=',')
{
printf("%i",pointer);
second[currentPointer]=NumBuf[pointer];
currentPointer++;
pointer++;
}
printf("Student Second : %.10s \n",second);



}
else
{
printf("MY SPOON IS TOO BIG\n");
}

}

printf("**** UP IS OVER HERE!!!\n");








}

fclose(pFile);



}

You are not null-terminating your strings. Add something like
for the studNum and similar lines for first and second. You will need to increase the length of the studNum array to 9 to hold the extra 0 character.

This is exactly what MaHuJa already posted before.