#include <stdio.h> #include <stdlib.h> #include <string.h> void InsertStudent(char*** students,int*** marks); void DeleteStudent(char*** students,int*** marks); void SortClass(char** students,int** marks); void ShowClass(char** students,int** marks); void EditMarks(char** students,int** marks); char* ReadLine(); #define merror(a) {printf("memory allocation error %d\n",a);exit(1);}
/* function main ----------------------------------------------- */ int main() {
char** students = NULL; int** marks = NULL; char line[100]; int menu;
while(1) { printf("Enter (1) to Add a Student to Class List\n" " (2) to Delete a Student from Class List\n" " (3) to show Class List\n" " (4) to Edit marks of a Student\n" " (5) to Quit\n"); fflush(stdout); gets(line); if (sscanf(line,"%d",&menu) != 1) { printf("incorrect entry"); continue; } if (menu < 1 || menu > 5) { printf("incorrect selection"); continue; }
if (menu == 1) InsertStudent(&students,&marks); else if (menu == 2) DeleteStudent(&students,&marks); else if (menu == 3) ShowClass(students,marks); else if (menu == 4) EditMarks(students,marks); else break; }/*endwhile*/
return 0;
}/*end main*/
/* function InsertStudent ------------------------------------ */ /*This function prompts the user to enter a new student name. The precise form of the prompt is Enter Student Name to be added to Class List: Then this function reads the name from standard input. But it must be able to read any name of any size!! Thus you have to allocate memory (using malloc()) to read the input into, and if it is not big enough, must use realloc() to extend it. You are not allowed to allocate more than 10 bytes in one allocation or extend your segment by more than 10 bytes in one call to realloc(). Do not forget to deallocate the memory before exiting the function!
Once the function has the name to be entered, it traverses the array student to find out if the name is already there. If so, the function displays a warning message "student xxx already in the class list" and terminates ( where xxx is the name of the student). If the name is not in the array, the array students is extended by one item (using realloc()) and a copy of the string with the name is "placed" there. Also the array marks is extended by one row (using realloc()) and all five marks in that row are set to -1. Then updated arrays students and marks are passed to SortClass() so they can be sorted alphabetically, as you are required to keep the class list and the list of marks in alphabetical order.
Note that both students and marks are passed to this function "by reference", for this function on occasions must be able to modify the value stored in the pointer student (in main()) - when putting there the very first student or when realloc() possibly "moves" the array in the memory somewhere else. The same applies to marks.*/ void InsertStudent(char*** students,int*** marks) { char* buf; int found, i, j, size; char** students1; int** marks1; students1 = *students; marks1 = *marks;
char *name; printf("Enter Student Name to be added to Class List:\n"); fflush(stdout); name = ReadLine();
if (students1 == NULL) { if ((students1 = (char**) malloc(2*sizeof(char*))) == NULL)merror(2); if ((students1[0] = (char*) malloc(strlen(name)+1)) == NULL)merror(3); strcpy(students1[0],name);
students1[1] = NULL; if ((marks1 = (int**) malloc(2*sizeof(int*))) == NULL)merror(4); if ((marks1[0] = (int*) malloc(5*sizeof(int))) == NULL)merror(5); marks1[0][0]=marks1[0][1]=marks1[0][2]=marks1[0][3]=marks1[0][4]=-1; marks1[1] = NULL;
*students = students1; *marks = marks1; return; }
/* do we have the student yet ? */ for(found = i = 0; students1[i] != NULL; i++) { if (strcmp(students1[i],name) == 0) { found = 1; break; } }
if (found) { printf("student %s already in the class list\n",name); return; }
/* so it is not in the class list yet */
students1 = (char**) realloc((void*)students1,(i+2)*sizeof(char*)); if (students1 == NULL) merror(6); if ((students1[i] = (char*) malloc(strlen(name)+1)) == NULL) merror(7); strcpy(students1[i],name);
students1[i+1] = NULL;
free((void*) name);
if ((marks1 = (int**) realloc((void*)marks1,sizeof(int*)*(i+2))) == NULL) merror(8); if ((marks1[i] = (int*) malloc(5*sizeof(int))) == NULL) merror(9); marks1[i][0]=marks1[i][1]=marks1[i][2]=marks1[i][3]=marks1[i][4]=-1; marks1[i+1] = NULL;
SortClass(students1,marks1);
*students = students1; *marks = marks1; }
/* function DeleteStudent ------------------------------------ */
/*This function prompts the user to enter a student name to be deleted.The precise form of the prompt is
Enter Student Name to be deleted from Class List: Then this function reads the name from standard input. But it must be able to read any name of any size!! Thus you have to allocate memory (using malloc()) to read the input into, and if it is not big enough, must use realloc() to extend it. You are not allowed to allocate more than 10 bytes in one allocation or extend your segment by more than 10 bytes in one call to realloc(). Do not forget to deallocate the memory before exiting the function! Note that this part of the code is the same as in InsertStudent(), so you can either copy it or write a function that would do it for both.
Once the function has the name to be deleted, it traverses the array student to find out if it is there. If not, a warning message is displayed "student xxx not in the class list" and the function terminates. If it is found (say its is students[d]), a dynamic one-dimensional array one item shorter than students is created and the strings from the array students are "unhooked" from the arrays students and "hooked" to the new array with the exception of the string to be deleted (don't forget that the "deleted" string must be deallocated). Now deallocate the array students and make the pointer student point to the new array. As you can see we have the "same" array of string as before, but with one string deleted. You must do the same with the array marks, for you must delete completely d-th row (so it did correspond to student[d] which we deleted).
Note that both students and marks are passed to this function "by reference", for this function on must be able to modify the value stored in the pointer student (in main()) - when a student name is deleted. The same aplies to marks.*/
void DeleteStudent(char*** students,int*** marks) { }
/* function SortClass --------------------------------------------------- */ /*In this function you sort the strings in the array students alphabetically (lexico-graphically) using a simple bubble sort and the comparison function for strings strcmp(). Do not forget that as you are changing the order of strings in students, you must be changing the order of rows in the arry marks. Note, that when sorting the array students, and when you want to switch ith- string with the (i+1)st-string, all you have to do is switch the pointers, you do not have to touch the strings themselves.
Note that both students and marks are passed to this function "by value", for this function does not need to modify the value stored in the pointer student. The same applies to marks.*/
void SortClass(char** students,int** marks) {
}
/* function ShowClass ------------------------------------------------- */ /*In this function you display on the screen each student in the class and his/her 5 marks on a line. If the mark is -1 display a space instead. After the name of student display : and separate the marks by ,
Note that both students and marks are passed to this function "by value", for this function does not need to modify the value stored in the pointer student. The same applies to marks.*/ void ShowClass(char** students,int** marks) {
}
/* function EditMarks ----------------------------------------------- */ /*This function prompts the user to enter a student name whose marks are to be edited. The precise form of the prompt is Enter Student Name whose marks are to be edited:
Then this function reads the name from standard input. But it must be able to read any name of any size!! Thus you have to allocate memory (using malloc()) to read the input into, and if it is not big enough, must use realloc() to extend it. You are not allowed to allocate more than 10 bytes in one allocation or extend your segment by more than 10 bytes in one call to realloc(). Do not forget to deallocate the memory before exiting the function! Note that this part of the code is the same as in InsertStudent() and DeleteStudent(), so you can either copy it or write a function that would do it for all three.
If the student is not found in the array students, a warning message "student xxx not in the Class List" is displayed on the screen and the function terminates. If it is found, the students name followed by : and his/her five marks are displayed (again, -1 must be shown as a space, as in ShowClass()). Let us assume that the student in question has marks 10,-1,20,15,5
Then the function displays a prompt to the user for the first mark to leave the 1st mark 10 unchanged press<enter> otherwise type the new mark and press<enter> and reads the user's reply using gets() into a character arrays of size 80. Then it uses sscanf() on that array to "extract" the response. Then the function displays a prompt to the user for the second mark to leave the 2nd mark unchanged press<enter>otherwise type the new mark and press<enter> and reads the user's reply using gets() into a character arrays of size 80. Then it uses sscanf() on that array to "extract" the response. Etc. for the third, fourth, and fifth.
Note that both students and marks are passed to thisfunction "by value", for this function does not need to modify the value stored in the pointer student. The same applies to marks.*/ void EditMarks(char** students,int** marks) { }
char* ReadLine() { char *buf; int i, j, size; if ((buf = (char*) malloc(10)) == NULL) merror(0); size = 10; j = -1; while(1) { for(i = 0; i < 10; i++) { buf[++j] = getchar(); if (buf[j] == '\n') { buf[j] = '\0'; break; } }/*endfor*/
if (i == 10 && buf[j] != '\0') { size += 10; if ((buf = (char*) realloc((void*)buf,size)) == NULL) merror(1); continue; } break; }/*endwhile*/ return buf;
}/*end ReadLine*/
