//Keven Hyppolite
//EGN3211
//Homework7B

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

FILE *hwdfp;
//hardware dat file pointer

struct hws{
//hardware structure
int rn;
//record number
char ts[30];
//tools in the struct
int quantity;
//quantity of tools
double cost;
//cost of tools
};
//struct for the hardware

int yourchoice(void);
//This will ask the questions

void storetxt(FILE *reader);
//This will store the text
//reader points to file type

void UPDATE(FILE *fPtr);
//This function will update the function

void ADD(FILE *fPtr);
//Adds to record

void DELETE(FILE *fPtr);
//Delete's record

int main(){
FILE *hwdfp;
int choice;

    if((hwdfp = fopen("hardware.dat", "rb+")) == NULL){
        printf("File could not be opened.\n");
        }else{
    while ((choice = yourchoice()) != 9){
        switch (choice){
    case 1:
        storetxt(hwdfp);
    break;
//stores formatted txt file
    case 2:
        UPDATE(hwdfp);
    break;
//update
    case 3:
        ADD(hwdfp);
    break;
//add
    case 4:
        DELETE (hwdfp);
    break;
//delete
    default:
printf("Invalid Input\n");
break;
//9 terminates program, everything else in invalid
}
} 
fclose(hwdfp); 
} 
return 0; 
}
//main function controls switch
//Input 9 will terminate program

void storetxt(FILE *reader){
FILE *txt;
//pointer to txt file

struct hws hardware = {0, "", 0,0.0};
//intialized structre variables

if ((hwdfp = fopen("hardware.txt", "rb+")) == NULL ){
printf("File could not be opened.\n");
    }else{
        rewind(reader);
        fprintf(txt, "%-6s%-10s%-8s%-8s\n",
        "Record#", "Tool name", "Quantity", "Cost");

    while (!feof(reader)){
        fread(&hardware, sizeof(struct hws),1, reader );
    if (hardware.rn != 0){
        fprintf(txt, "%d%s%d%0.2f\n", hardware.rn, hardware.ts, 
                hardware.quantity, hardware.cost);
    }
} 
    fclose(txt);
    }
}

void UPDATE (FILE *fPtr){
int record; 
struct hws hardware = {0, "", 0,0.0};
printf("Enter record to update (0-100): ");
scanf("%d", &record);
fseek(fPtr, (record - 1) *sizeof(struct hws), SEEK_SET);
fread(&record, sizeof(struct hws), 1, fPtr);

if (hardware.rn == 0){
printf( "Record #%d has no information.\n", record);
    }else{ 
        printf("Enter new tool name, quantity,cost \n?");
        scanf("%s%d%f", hardware.ts, hardware.quantity, hardware.cost);
        fseek(fPtr, (record - 1) *sizeof(struct hws), SEEK_SET);
        fwrite(&hardware, sizeof(struct hws), 1, fPtr);
        }
}
//Update Record, basically changing variables

void DELETE(FILE *fPtr){
struct hws hardware;
struct hws remover = {0, "", 0,0.0};
int rn;

printf( "Enter record number to delete (0-100): ");
scanf("%d", &rn);
fseek(fPtr, (rn - 1) *sizeof(struct hws), SEEK_SET);
fread(&hardware, sizeof(struct hws), 1,fPtr);

if (hardware.rn == 0){
    printf ("Record %d does not exist.\n", rn);
        }else{
            fseek(fPtr,(rn - 1) *sizeof(struct hws), SEEK_SET);
            fwrite(&remover, sizeof(struct hws), 1, fPtr);
            }
}
//Delete's New record

void ADD(FILE *fPtr){
struct hws hardware = {0, "", 0,0.0};
int rn;
printf("Enter record number to create (1-100) : ");
scanf("%d", &rn);
fseek(fPtr, (rn - 1) *sizeof(struct hws), SEEK_SET);
fread(&hardware, sizeof(struct hws), 1, fPtr);
    if(hardware.rn != 0){
        printf("Record already exists");
        }else{
            printf("Enter tool name, quantity, cost\n");
            scanf("%s%d%0.2f", hardware.ts, hardware.quantity, hardware.cost);
            fseek(fPtr,(rn - 1) *sizeof(struct hws), SEEK_SET);
            fwrite(&hardware, sizeof(struct hws), 1, fPtr);
}
//Enter data you want to ADD

}
//Adds new record

int yourchoice(void){
int ch;
    printf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n\n%s",
    "Your choices are:",
    "1 - STORE a formatted text file of inventoried tools called",
    " hardware.txt for printing", "2 - UPDATE a tool record", 
    "3 - ADD a new tool record", "4 - DELETE a tool record", 
    "5 - DISPLAY a tool record", "9 - END program", "Enter your choice: ");
    scanf("%d", &ch);
    return ch;
}
//Display's choices, and you decide 

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About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}  

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition); 

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}