looking for advice

[bbcat]

To practice C language,I began to develop a simple project which
implements the management of students' information.I have worked it for
one week. I plan to finish it for two weeks.
Are there some experienced friends who would like to read my source
code and give some advice to me.tks :)

---------------------------------------------------------
main.c
---------------------------------------------------------
#include <stdio.h>
#include <string.h>
#include "logic.h"

const char *filename = "student.da t";

main(void)
{
int menu_id = 99;
int student_num = 0;
struct node *phead = NULL;

void load_menu();
void func_menu_new(s truct node *phead);// new a student
void func_menu_searc h(struct node *phead);
void func_menu_edit( struct node *phead);
void func_menu_print (struct node *phead);
void func_menu_exit( struct node *phead);

load_menu();
phead = init();

if(read_datafil e(phead,filenam e) == 1)
{
printf(" The file %s doesn't exist! \n",filename) ;
}

student_num = get_student_num (phead);
printf(" there are %d students' information.\n" ,student_num);

tag_start: scanf("%d",&men u_id);

switch (menu_id)
{
case 0:
func_menu_exit( phead);
break;
case 1:
func_menu_new(p head);
break;
case 2:
func_menu_searc h(phead);
break;
case 3:
func_menu_edit( phead);
break;
case 4:
func_menu_print (phead);
break;
default:
printf("Sorry,O nly 0--4 can be chosen,please input again :)\n");
}
if(menu_id !=0)
goto tag_start;

}

void load_menu()
{
clrscr();

printf("\n");
printf("\n");
printf(" Welcome to Use Student System \n");
printf(" =============== ======menu===== =============== =\n");
printf(" Input a student's informations... ............... 1\n");
printf(" Search student's informations... ............... .2\n");
printf(" Modify student's informations... ............... .3\n");
printf(" Print student's informations... ............... ..4\n");
printf(" exit system......... ............... .............0\ n");
printf("\n");
}

void func_menu_new(s truct node *phead)
{
struct student *pnewstudent = (struct student *)(sizeof(struc t
student));

printf("please input a new student's information\n") ;
scanf("%d",&(pn ewstudent->id));
scanf("%s",pnew student->name);

student_add(phe ad,pnewstudent) ;

printf("you have input a student's informations successfully!\n ");

free(pnewstuden t);
pnewstudent = NULL;
}

void func_menu_print (struct node *phead)
{
struct node *ptemp;
int student_num;

ptemp = phead;
student_num = get_student_num (phead);
printf(" All Student Information\n") ;
printf(" =============== =============== ===\n");
printf(" there are %d students' information.\n" ,student_num);
printf("| Student ID ");
printf("|");
printf(" Student name |\n");

while(ptemp->next != NULL)
{
printf("| %10d ",ptemp->next->stu_info.id) ;
printf("| %14s |\n",ptemp->next->stu_info.name) ;
ptemp = ptemp->next;
}
ptemp = NULL;
}

void func_menu_exit( struct node *phead)
{
if(save_to_data file(phead,file name) == 0)
{
printf(" All students' informations are saved!");
}

free_memo(phead );
}

void func_menu_searc h(struct node *phead)
{
int search_type;
int search_id;
char search_name[20];
struct node *psearch;

printf("Search by what?\n");
printf(" 1: student ID\n");
printf(" 2: student name\n");
scanf("%d",&sea rch_type);

while((search_t ype != 1) && (search_type != 2))
{
printf("sorry, please choose 1 or 2\n");
scanf("%d",&sea rch_type);
}

switch (search_type)
{
case 1:
{
printf("please input the student's ID\n");
scanf("%d",&sea rch_id);
psearch = search_by_id(se arch_id,phead);
if(psearch == NULL)
{
printf("sorry there are no student infomation with ID
=%d\n",search_i d);
}
else
{
printf(" %d :",psearch->stu_info.id) ;
printf(" %s\n",psearch->stu_info.name) ;
}
}
break;
case 2:
{
printf("please input the student's name\n");
scanf("%s",sear ch_name);
psearch = search_by_name( search_name,phe ad);

if(psearch == NULL)
{
printf("sorry there are no student infomation with name =
%d\n",search_na me);
}
else
{
printf(" %d :",psearch->stu_info.id) ;
printf(" %s\n",psearch->stu_info.name) ;
}
}
break;
default:
printf("error occurs");
}
psearch = NULL;
}

void func_menu_edit( struct node *phead)
{
int stu_id,stu_id_n ew;
char stu_name_new[20];
struct node *psearch;

printf(" Please input the ID of the student you want to edit.\n");
scanf("%d",&stu _id);
psearch = search_by_id(st u_id,phead);

if(psearch == NULL)
{
printf("sorry there are no student infomation with ID
=%d\n",stu_id);
}
else
{
printf(" %d :",psearch->stu_info.id) ;
printf(" %s\n",psearch->stu_info.name) ;
}

printf(" Please input the student's new information!\n" );
scanf("%d",&stu _id_new);
scanf("%s",stu_ name_new);
psearch->stu_info.id = stu_id_new;
strcpy(psearch->stu_info.name, stu_name_new);

printf("You update a student's information successfully!\n ");
psearch = NULL;
}


--------------------------------------------------------
logic.c
-------------------------------------------------------
#include "logic.h"
#include <stdio.h>
struct node * init()
{
struct node * ptemp;

ptemp = (struct node*)malloc(si zeof(struct node));
ptemp->next = NULL;

return ptemp;
}

void student_add(str uct node *phead,struct student *pnewstudent)
{
struct node *pnew,*ptemp;

ptemp = phead;
pnew = (struct node*)malloc(si zeof(struct node));
pnew->stu_info.id = pnewstudent->id;
strcpy(pnew->stu_info.name, pnewstudent->name);

while(ptemp->next != NULL)
{
ptemp = ptemp->next;
}
ptemp->next = pnew;
pnew->next = NULL;
pnew = NULL;
ptemp = NULL;
}

int get_student_num (struct node *phead)
{
struct node *ptemp;
int student_num = 0;

ptemp = phead->next;

while(ptemp != NULL)
{
ptemp = ptemp->next;
student_num ++;
}
ptemp = NULL;
return student_num;
}

int save_to_datafil e(struct node *phead,char *filename)
{
struct node *ptemp;
int student_num;
FILE *fp;

ptemp = phead;
student_num = get_student_num (phead);
fp=fopen(filena me, "w");
fprintf(fp,"%d\ n",student_num) ;

while(ptemp->next != NULL)
{
fprintf(fp, "%d", ptemp->next->stu_info.id) ;
fprintf(fp, "%s\n", ptemp->next->stu_info.name) ;
ptemp = ptemp->next;
}

ptemp = NULL;
fclose(fp);
return 0;
}

int read_datafile(s truct node *phead,char *filename)
{
struct node *pnew,*ptemp;
FILE *fp;
int student_num;

ptemp = phead;
fp = fopen(filename, "r");

if(fp == NULL)
{
return 1;
}

fscanf(fp,"%d", &student_num );

while(student_n um > 0)
{
pnew = (struct node*)malloc(si zeof(struct node));
fscanf(fp,"%d", &(pnew->stu_info.id) );
fscanf(fp,"%s", pnew->stu_info.name) ;
ptemp->next = pnew;
ptemp = ptemp->next;
student_num --;
}
ptemp = NULL;
pnew = NULL;
fclose(fp);
return 0;
}

void free_memo(struc t node *phead)
{
struct node *ptemp,*pnext;

ptemp = phead->next;

while(ptemp != NULL)
{
pnext = ptemp->next;
free(ptemp);
ptemp = pnext;
}

free(phead);
phead = NULL;
ptemp = NULL;
pnext = NULL;
}

struct node * search_by_id(in t search_id,struc t node *phead)
{
int id = search_id;
struct node *ptemp,*psearch ;

psearch = NULL;
ptemp = phead->next;

while(ptemp != NULL)
{
if(ptemp->stu_info.id == id)
{
psearch = ptemp;
}
ptemp = ptemp->next;
}

return psearch;
}

struct node * search_by_name( char search_name[20],struct node *phead)
{
struct node *ptemp,*psearch ;

psearch = NULL;
ptemp = phead->next;

while(ptemp != NULL)
{

if(strcmp(ptemp->stu_info.name, search_name) == 0)
{
psearch = ptemp;
}
ptemp = ptemp->next;
}

return psearch;
}

-----------------------------------------------------------
logic.h
-----------------------------------------------------
#ifndef LOGIC_H
#define LOGIC_H

#define LEN sizeof(struct student)

struct student
{
int id;
char name[20];
};

struct node
{
struct student stu_info;
struct node *next;
};

extern struct node * init();
extern int read_datafile(s truct node *phead,char *filename);
extern int get_student_num (struct node *phead);
extern int save_to_datafil e(struct node *phead,char *filename);
extern void student_add(str uct node *phead,struct student
*pnewstudent);
extern void free_memo(struc t node *phead);
extern struct node * search_by_id(in t search_id,struc t node *phead);
extern struct node * search_by_name( char search_name[20],struct node
*phead);
#endif

[Arthur J. O'Dwyer]

On Wed, 16 Mar 2005, bbcat wrote:

To practice C language,I began to develop a simple project which
implements the management of students' information.I have worked it for
one week. I plan to finish it for two weeks.
Are there some experienced friends who would like to read my source
code and give some advice to me.tks :)

Yes. His name is 'gcc', and you can find him online or on your hard
disk. Try

gcc -W -Wall -ansi -pedantic -O3 -c logic.c
gcc -W -Wall -ansi -pedantic -O3 -c main.c

You will find many trivial yet fatal errors (such as forgetting to
prototype 'malloc' before using it), as well as several errors that
are just plain dumb (such as passing a string to 'printf("%d")')
and several stylistic booboos (such as forgetting to write
'int main(void)' instead of just 'main(void)').
Fix the mistakes the compiler tells you, and then post again.
Oh, and try not to post so *MUCH*. Put the code in three separate
files on your Web site, and post the URL. Then people won't have to
cut and paste so much in order to help you. If you make it hard for
people to help you, they usually won't.

Finally, don't use hard tabs (ASCII character 0x09) in Usenet posts,
or in code you expect a lot of people to read. They can get horribly
mangled by Usenet, and also by text editors (some of which think one
tab is eight spaces, some four, some three, some two, and some even
weirder numbers). Run 'detab' on your source code before posting it.

-Arthur

[Thomas Matthews]

bbcat wrote:

To practice C language,I began to develop a simple project which
implements the management of students' information.I have worked it for
one week. I plan to finish it for two weeks.
Are there some experienced friends who would like to read my source
code and give some advice to me.tks :)

---------------------------------------------------------
main.c
---------------------------------------------------------
#include <stdio.h>
#include <string.h>
#include "logic.h"

const char *filename = "student.da t"; Do you want a const pointer to constant data?
const char * const filename = "student.da t";

main(void) The main() function returns an int. Declare it properly:
int main(void)
{
int menu_id = 99;
int student_num = 0;
struct node *phead = NULL;

void load_menu();
void func_menu_new(s truct node *phead);// new a student
void func_menu_searc h(struct node *phead);
void func_menu_edit( struct node *phead);
void func_menu_print (struct node *phead);
void func_menu_exit( struct node *phead); Declarations don't need to be encapsulated inside a function.
A popular style is to place all the declarations before the
main() function. Some people even alphabetize the list.

I suggest you place the declarations into a header file
with explanations of what they do, and their return values,
if any.

load_menu();
phead = init();

if(read_datafil e(phead,filenam e) == 1)
{
printf(" The file %s doesn't exist! \n",filename) ;
} Interesting, two points here:
1. A read failure or open failure does not indicate that the file
does not exist, only that the open failed. For example, the
file may exist, but your program doesn't have access rights to
open it.
2. The program announces the file doesn't exist but continues anyway.
Very bad karma.

student_num = get_student_num (phead);
printf(" there are %d students' information.\n" ,student_num);

tag_start: scanf("%d",&men u_id); Input from a user without a prompt.
More bad karma.
Label usage, could be eliminated. Depends on you allergy level
to gotos.

switch (menu_id)
{
case 0:
func_menu_exit( phead);
break;
case 1:
func_menu_new(p head);
break;
case 2:
func_menu_searc h(phead);
break;
case 3:
func_menu_edit( phead);
break;
case 4:
func_menu_print (phead);
break;
default:
printf("Sorry,O nly 0--4 can be chosen,please input again :)\n");
}
if(menu_id !=0)
goto tag_start;

} Try this:
typedef void (*Menu_Function _Pointer)(struc t node *);
struct Menu_Item
{
unsigned int value;
const char * prompt; /* or description */
Menu_Function_P ointer action;
};

const struct Menu_Item Main_Menu[] =
{
{0,
"exit system......... ............... .............0\ n",
func_menu_exit} ,
{1,
"Input a student's informations... ............... 1\n",
func_menu_new},
{2,
"Search student's informations... ............... .2\n",
func_menu_searc h}
};
const unsigned int Num_Main_Menu_I tems =
sizeof(Main_Men u) / sizeof(Main_Men u[0]);

void load_menu(void)
{
static const char * Menu_Header =
"\n"
"\n"
" Welcome to Use Student System\n"
" =============== ======menu===== =============== =\n";
unsigned int i;
fwrite(Menu_Hea der, sizeof(Menu_Hea der), 1, stdout);
for (i = 1; i < Num_Main_Menu_I tems; ++i)
{
printf(" %s", Main_Menu[i].prompt);
}
printf("\n");
return;
}

unsigned int process_menu(st ruct * phead)
{
unsigned int selection;
unsigned int index;

do
{
scanf("%d", &selection);
for (index = 0; index < Num_Main_Menu_I tems; ++index)
{
if (selection == Main_Menu[index].value)
{
(Main_Menu[index].action)(phead) ;
break; /* exit the "for" loop */
}
}
if (index >= Num_Main_Items)
{
printf("Sorry,O nly 0--%d can be chosen,please input again :)\n",
Num_Main_Menu_I tems - 1);
}
} while (index >= Num_Main_Items) ;
return selection;
}

void load_menu()
{
clrscr();

printf("\n");
printf("\n");
printf(" Welcome to Use Student System \n");
printf(" =============== ======menu===== =============== =\n");
printf(" Input a student's informations... ............... 1\n");
printf(" Search student's informations... ............... .2\n");
printf(" Modify student's informations... ............... .3\n");
printf(" Print student's informations... ............... ..4\n");
printf(" exit system......... ............... .............0\ n");
printf("\n");
}

[snip]

I suggest making your linked list into separate
functions so you can use it for other projects. ;-)

--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.l earn.c-c++ faq:
http://www.comeaucomputing.com/learn/faq/
Other sites:
http://www.josuttis.com -- C++ STL Library book
http://www.sgi.com/tech/stl -- Standard Template Library

[bbcat]

thank Thomas Matthews and Arthur J. O'Dwyer for your advice very much
:-)