School Project Personal Dairy Management in C programming

This project is similar to the project Contact Management in C. In this project, I am reusing all the code from it. I created this Personal Dairy Management project just by renaming printed messages, adding a few functions, and modifying existing functions slightly.

Please go through the Contact Management project if you haven't. In this project, I have explained the techniques of file handling in C.

So, in this project, I will explain the changes that I have made.

Let's start with describing data structure.

// Define Constant Variables
#define ESC 27
#define REF_SZ 10
#define DATE_SZ 64
#define MIN_TEXT_SZ 50
#define MAX_TEST_SZ 500
#define READ_ARRAY_SZ 15
#define DATA_FILE "dataFile.dat"
#define TEMP_FILE "tempFile.dat"

//Define data structure

struct data{
    char refNum[REF_SZ]; //Unique reference number and auto-incremented
    char noteDate[DATE_SZ]; //Auto populated using system date and time
    char eventDate[DATE_SZ]; //Event date
    char location[MIN_TEXT_SZ]; //Location of event happened
    char eventDesc[MIN_TEXT_SZ]; //Event short description
    char notes[MAX_TEST_SZ]; //Notes of the Event
};

I am using 6 variables in a structure. The variable "refNum" will be unique and it is auto-increment. The variable "noteDate" is to store note added date and it is also auto-populated using system date and time. 

Other variables are:

• eventDate: Event date. It can be any format chosen by the user
• location: Location of event happened.
• eventDesc: Event short description.
• notes: Notes of the event. Maximum character is 500.

Although the variable refNum is auto-incremented, I haven't defined it as an integer. Rather than storing number value only, I decided to add '#R' as an initial character so that the unique reference value will look like "#R10001" instead of "1000".

To achieve this we have to create two separate small functions which I will describe below.

Function: getNextRef()

//Get next reference number

int getNextRef(){

    struct data a;
    int num=0;
    fp = fopen(DATA_FILE,"rb");

    if(fp!= NULL){

        fseek(fp,0,SEEK_END);

        fseek(fp,ftell(fp)-sizeof(a),0);
        fread(&a,sizeof(a),1,fp);

        // converting string to number
        for (int i = 0; a.refNum[i + 2] != '\0'; i++) {
            num = num * 10 + (a.refNum[i + 2] - 48);
        }
        fclose(fp);
        return num;

    } else {

        return 10000;
    }
}

This function will read the last item from the file and read the reference number which is the previous reference number and also the highest value. It will remove the first two characters, convert the remaining numbers into an integer data type, and return it. This function will be executed at the start of the application so if it does not find a file then it will return 1000. 

Function: calRefNum(char *buff, int num)

//Calculate next reference number
static void calRefNum(char *buff, int num){

    char tmpRef[REF_SZ];
    char refNum[REF_SZ] = {'#','R'};
    sprintf(tmpRef,"%d",num);
    strcat(refNum, tmpRef);
    strcpy(buff,refNum);
}

This function converts the reference number into char data type, concatenates with the "#R" initial character, and assigns it to a character pointer which is used while adding notes.

Apart from these changes I have made a few changes in readData(), add(), and view() functions. Once you compile and run it you will understand the changes.

Please download the source code from the GitHub Download Source Code.