Thread: Linked List problem

How do I write a C program that will use a linked list of structures to
represent the customers of a bank?
Each structure has to be designed
to hold information regarding a persons
how would i start? ima newbie to this and i dont quite get it

(1) Last name
(2) First name
(3) Middle initial
(4) Social Security number
(5) Bank balance

Looks like homework to me.....

but anyway first define the structure:

[CODE]
typedef struct customer
{
char fname[20];
char lname[20];
char initial;
long socialnum;
double balance;
struct customer *next;
} CUSTOMER;

then create a pointer to this:

CUSTOMER *bankrecords;

assign memory:

bankrecords = (CUSTOMER *) malloc(sizeof(CUSTOMER));

then do what ya want with it ie to add a name do:

strcpy(bankrecords->fname,"FRED");

to add a new customer go to the end of the list, ie
tempptr = bankrecords;
while(tempptr->next!=NULL)
tempptr=tempptr->next;

then assign more memory
tempptr->next = (CUSTOMER *) malloc(sizeof(CUSTOMER));
and repeat the adding, I'm sure you can work out the rest otherwise its not really homework where ya learning anything at all.
Hope this helps

thank you all very much, you have been of great help, it is a homework assignment but becuase im a biology major and not a computer science major its difficult for me but im working on it

i have a problem i need to be able to read data from a file and im not sure how to do it. This is what i have so far.

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

struct customer
{
char fname[20];
char lname[20];
char initial;
long socialnum;
double balance;
struct customer *next;
};


int main(void)
{
FILE *infile;


infile= fopen("data.dat","r");




fclose(data.dat)
return 0;
}

those will not work when im trying to read the data into a structure. I have a data file that has info like this:

Moon Warren H 637801463 19473.08

So it has to be able to read the first name into bankrecords.fname and last name into bankrecords.lname and so on.

fscanf will work perfectly, just do:

Code:

fscanf(infile,"%s %s %c %d %f",(*bankrecords)->fname,(*bankrecords)->lname,bankrecords->initial,bankrecords->account,bankrecords->balance);

think the pointers and *'s are right not 100% but pretty sure about the first two, and slightly to lazy to double check

p.s. make sure you assign the memory before you do the fscanf or you'll have problems.

When i use
bankrecords = (CUSTOMER *) malloc(sizeof(CUSTOMER));
it gives me errors

you need to assign your structure a name, if you have a look at the code example I gave it will work:

Code:

typedef struct customer 
{ 
  char fname[20]; 
  char lname[20]; 
  char initial; 
  long socialnum;
  double balance; 
  struct customer *next; 
} CUSTOMER;

the last line : } CUSTOMER;
allow you to treat this as a standard data type and decalre variables like:
CUSTOMER john;
and then you have a variable called john.
alternatevly you could use:

bankrecords = (struct customer *) malloc(sizeof(struct customer));
I think, but the first way will work and make it heaps easier to assign new variables, etc.

I have this and it says my variables are not identified.

[code]

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

struct customer
{
char fname[20];
char lname[20];
char initial;
long socialnum;
double balance;
struct customer *next;
};


int main()
{
FILE *infile;
struct customer *bankrecords;
int count=1;

bankrecords = (CUSTOMER *) malloc(sizeof(CUSTOMER));


if((infile = fopen("data.dat","r")) == NULL) {
printf("Data file could not be opened.\n");
exit(1);
}
infile=fopen("data.dat","r");
printf("NUM ADDRESS LAST\tFIRST MI\tSSN BALANCE NEXT\n");
printf("-----------------------------------------------------\n");
while(!feof(infile)) {
//fread(&bankrecords,sizeof(struct customer),1,infile);
fscanf(infile,"%s %s %c %d %f",bankrecords.fname,bankrecords.lname,bankrecord s.initial,bankrecords.socialnum,bankrecords.balanc e);

printf("\n %s",bankrecords.fname);


}


fclose(infile);
return 0;
}

[code\]

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

typedef struct customer
{
char fname[20];
char lname[20];
char initial;
long socialnum;
double balance;
struct customer *next;
}CUSTOMER;


int main()
{
FILE *infile;

int count=1;

bankrecords = (struct customer *) malloc(sizeof(struct customer));


if((infile = fopen("data.dat","r")) == NULL) {
printf("Data file could not be opened.\n");
exit(1);
}
infile=fopen("data.dat","r");
printf("NUM ADDRESS LAST\tFIRST MI\tSSN BALANCE NEXT\n");
printf("-----------------------------------------------------\n");
while(!feof(infile)) {
//fread(&bankrecords,sizeof(struct customer),1,infile);
fscanf(infile,"%s %s %c %d %f",bankrecords.fname,bankrecords.lname,bankrecord s.initial,bankrecords.socialnum,bankrecords.balanc e);

printf("\n %s",bankrecords.fname);


}


fclose(infile);
return 0;
}

ok im gettin error messages that say.............

--------------------Configuration: lab5 - Win32 Debug--------------------
Compiling...
lab5.cpp
C:\Documents and Settings\All Users\Documents\lab5.cpp(22) : error C2065: 'bankrecords' : undeclared identifier
C:\Documents and Settings\All Users\Documents\lab5.cpp(22) : error C2440: '=' : cannot convert from 'struct customer *' to 'int'
This conversion requires a reinterpret_cast, a C-style cast or function-style cast
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2228: left of '.fname' must have class/struct/union type
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2228: left of '.lname' must have class/struct/union type
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2228: left of '.initial' must have class/struct/union type
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2228: left of '.socialnum' must have class/struct/union type
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2228: left of '.balance' must have class/struct/union type
C:\Documents and Settings\All Users\Documents\lab5.cpp(36) : error C2228: left of '.fname' must have class/struct/union type
Error executing cl.exe.

lab5.obj - 8 error(s), 0 warning(s)

ok where are you gettin john->balance from? and i still get errors with my code

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

typedef struct customer
{
char fname[20];
char lname[20];
char initial;
long socialnum;
double balance;
struct customer *next;
}CUSTOMER;


int main()
{
FILE *infile;

int count=1;

CUSTOMER bankrecords = (struct customer *) malloc(sizeof(struct customer));


if((infile = fopen("data.dat","r")) == NULL) {
printf("Data file could not be opened.\n");
exit(1);
}
infile=fopen("data.dat","r");
printf("NUM ADDRESS LAST\tFIRST MI\tSSN BALANCE NEXT\n");
printf("-----------------------------------------------------\n");
while(!feof(infile)) {
//fread(&bankrecords,sizeof(struct customer),1,infile);
fscanf(infile,"%s %s %c %d %f",CUSTOMER bankrecords->fname,CUSTOMER bankrecords->lname,CUSTOMER bankrecords->initial,CUSTOMER bankrecords->socialnum,CUSTOMER bankrecords->balance);

printf("\n %s",bankrecords->fname);


}


fclose(infile);
return 0;
}

--------------------Configuration: lab5 - Win32 Debug--------------------
Compiling...
lab5.cpp
C:\Documents and Settings\All Users\Documents\lab5.cpp(22) : error C2440: 'initializing' : cannot convert from 'struct customer *' to 'struct customer'
No constructor could take the source type, or constructor overload resolution was ambiguous
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2275: 'CUSTOMER' : illegal use of this type as an expression
C:\Documents and Settings\All Users\Documents\lab5.cpp(13) : see declaration of 'CUSTOMER'
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2146: syntax error : missing ')' before identifier 'bankrecords'
C:\Documents and Settings\All Users\Documents\lab5.cpp(34) : error C2059: syntax error : ')'
C:\Documents and Settings\All Users\Documents\lab5.cpp(36) : error C2819: type 'customer' does not have an overloaded member 'operator ->'
C:\Documents and Settings\All Users\Documents\lab5.cpp(6) : see declaration of 'customer'
C:\Documents and Settings\All Users\Documents\lab5.cpp(36) : error C2227: left of '->fname' must point to class/struct/union
Error executing cl.exe.

lab5.obj - 6 error(s), 0 warning(s)