hey ive mostley got this working however im not sure if im reading the binary file correctly because for some reason its playing up, anyone able to give it a look over ?

also i know in my sort function, there is an issue with the comparing of the values (x compared to x-1 (which is null) but i cant work out how to fix it without screwing up my binary stuff.

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

int menu();
long findlocation(long);
void writetoindex(long);
void sort();

struct record 
	{        
		char name[20];
		int AcntNum;  
		float balance;
	}Accounts; 

void main()
{
	long acntchoice;
	
	do{
		printf("Enter Account Number: ");
		scanf("%d",&acntchoice);

		
		writetoindex(findlocation(acntchoice));

	}while(menu()!=2);
	
	sort();

	system("pause"); //OMG MORE RANDOM COMMENTS
}

int menu()
{
	int choice;

	printf("What Would you like to do ?\n");
	printf("1.\tEnter Account Numbers\n");
	printf("2.\tFinished Entering\n");
	printf("-->");
	scanf("%d",&choice);

	return choice;
}

long findlocation(long acntchoice)
{
	long location=0;
	bool found=false;
	FILE * fstream1;
	fstream1 =fopen("Accounts.txt","r");
	if (!fstream1)
	{
		printf("Unable to open file!");
		return 0;
	}
	else
	{
		fseek(fstream1, 0, SEEK_END);
		int filesize = ftell(fstream1);
		rewind(fstream1);
		int structsize=sizeof(Accounts);
	
		for(long i=0;i<filesize;i+=structsize)
		{
			fread(&Accounts,structsize,1,fstream1);
			if(Accounts.AcntNum==acntchoice)
			{
				location=i;
				found=true;
			}
			else if(((i+structsize)==filesize)&&found==false)
			{
				printf("Account Not Found!\n");
			}
		}


		fclose(fstream1);
		return location;
	}
	
}

void writetoindex(long acntchoice)
{
	FILE * fstream2;
	fstream2 =fopen("Index.txt","w");

	if (!fstream2)
	{
			printf("Unable to open file!");
	}
	else
	{
	fwrite(&acntchoice,sizeof(long),1,fstream2);
	
	fclose(fstream2);
	}

}

void sort()
{
	FILE * fstream2;
	fstream2 =fopen("Index.txt","r+");
	bool swap=true;
	fseek(fstream2, 0, SEEK_END);
	int filesize = ftell(fstream2);
	rewind(fstream2);
	int structsize=sizeof(long);
	int pass =0;
	long var1,var2=9999999;

	if (!fstream2)
	{
			printf("Unable to open file!");
	}
	else
	{
		while(pass<(filesize/structsize)&&swap==true)
		{
			swap=false;
			for(int i=0;i<(filesize/structsize);i++)
			{
				fseek(fstream2,i*structsize,SEEK_SET);
				fread(&var1,sizeof(long),1,fstream2);
				fseek(fstream2,(i*structsize)+1,SEEK_SET);
				fread(&var2,sizeof(long),1,fstream2);
				if(var2<var1)
				{
					fseek(fstream2,i*structsize,SEEK_SET);
					fwrite(&var2,sizeof(long),1,fstream2);
					fseek(fstream2,(i*structsize)+1,SEEK_SET);
					fwrite(&var1,sizeof(long),1,fstream2);
					swap=true;
				}

			}
			pass++;

		}


		fclose(fstream2);
	}
}

line 54 is opening the file in text mode, not binary mode. the open flag for binary mode is "rb". Same with lines 91 and 109. Opening the files in text mode on MS-Windows will result in incorrectly reading binary data due to the translation of CR/LF line terminating characters in text files.

ok ive fixed that, i thik there is an issue with my sort function now...

void sort()
{
	FILE * fstream2;
	fstream2 =fopen("Index.txt","a+b");
	bool swap=true;
	fseek(fstream2, 0, SEEK_END);
	int filesize = ftell(fstream2);
	rewind(fstream2);
	int structsize=sizeof(long);
	int pass =0;
	long var1,var2;

	if (!fstream2)
	{
			printf("Unable to open file!");
	}
	else
	{
		while(pass<(filesize/structsize)&&swap==true)
		{
			swap=false;
			for(int i=0;i<filesize;i+=structsize)
			{
				fseek(fstream2,i*structsize,SEEK_SET);
				fread(&var1,sizeof(long),1,fstream2);
				if((i*structsize)==((filesize-structsize)))
				{
					var2=var1;
				}
				else
				{
					fseek(fstream2,(i*structsize)+structsize,SEEK_SET);
					fread(&var2,sizeof(long),1,fstream2);
				}
				if(var2<var1)
				{
					fseek(fstream2,i*structsize,SEEK_SET);
					fwrite(&var2,sizeof(long),1,fstream2);
					fseek(fstream2,(i*structsize)+1,SEEK_SET);
					fwrite(&var1,sizeof(long),1,fstream2);
					swap=true;
				}

			}
			pass++;

		}


		fclose(fstream2);
	}
}
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