GUI with GTK - Project Coding

//Calculator.c file
#include<gtk/gtk.h>
#include<string.h> char input[20], operation, resultString[20];
float n1, n2, result;
GtkWidget *label2;
GtkWidget *entry; void onPButtonClicked() {
-strcpy(input, gtk_entry_get_text(GTK_ENTRY(entry)));
-strcat(input, "+");
-gtk_entry_set_text(GTK_ENTRY(entry), input);
} void onSButtonClicked() {
-strcpy(input, gtk_entry_get_text(GTK_ENTRY(entry)));
-strcat(input, "-");
-gtk_entry_set_text(GTK_ENTRY(entry), input);
}
void onDButtonClicked() {
-strcpy(input, gtk_entry_get_text(GTK_ENTRY(entry)));
-strcat(input, "/");
-gtk_entry_set_text(GTK_ENTRY(entry), input);
}
void onMButtonClicked() {
-strcpy(input, gtk_entry_get_text(GTK_ENTRY(entry)));
-strcat(input, "*");
-gtk_entry_set_text(GTK_ENTRY(entry), input);
}
void onClearButtonClicked() {
-gtk_entry_set_text(GTK_ENTRY(entry), "");
-strcpy(input, "");
} void onEqualButtonClicked() {
-strcpy(input, gtk_entry_get_text(GTK_ENTRY(entry)));
-sscanf(input, "%f%c%f", &n1, &operation, &n2);
-switch(operation) {
--case '+':
---result = n1+n2;
---break;
--case '-':
---result = n1-n2;
---break;
--case '*':
---result = n1*n2;
---break;
--case '/':
---result = n1/n2;
---break;
--default:
---onClearButtonClicked();
-}
-sprintf(resultString, "%.2f", result);
-gtk_label_set_text(GTK_LABEL(label2), resultString);
}
int main() { -gtk_init(NULL, NULL);
-GtkWidget *window;
-GtkWidget *mainBox;
-GtkWidget *entryBox;
-GtkWidget *resultBox;
-GtkWidget *operationsBox;
-GtkWidget *label1;
-GtkWidget *plusButton;
-GtkWidget *minusButton;
-GtkWidget *divideButton;
-GtkWidget *multiplyButton;
-GtkWidget *equalButton;
-GtkWidget *clearButton;
-GtkBuilder *builder;
-builder = gtk_builder_new_from_file("design.glade");
-window = GTK_WIDGET(gtk_builder_get_object(builder,"window"));
-mainBox = GTK_WIDGET(gtk_builder_get_object(builder, "mainBox"));
-entryBox = GTK_WIDGET(gtk_builder_get_object(builder, "entryBox"));
-resultBox = GTK_WIDGET(gtk_builder_get_object(builder, "resultBox"));
-operationsBox = GTK_WIDGET(gtk_builder_get_object(builder, "operationsBox"));
-label1 = GTK_WIDGET(gtk_builder_get_object(builder, "label1"));
-label2 = GTK_WIDGET(gtk_builder_get_object(builder, "label2"));
-plusButton = GTK_WIDGET(gtk_builder_get_object(builder, "plusButton"));
-minusButton = GTK_WIDGET(gtk_builder_get_object(builder, "minusButton"));
-divideButton = GTK_WIDGET(gtk_builder_get_object(builder, "divideButton"));
-multiplyButton = GTK_WIDGET(gtk_builder_get_object(builder, "multiplyButton"));
-equalButton = GTK_WIDGET(gtk_builder_get_object(builder, "equalButton"));
-entry = GTK_WIDGET(gtk_builder_get_object(builder, "entry"));
-clearButton = GTK_WIDGET(gtk_builder_get_object(builder, "clearButton"));
-g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
-g_signal_connect(plusButton, "clicked", G_CALLBACK(onPButtonClicked), NULL);
-g_signal_connect(minusButton, "clicked", G_CALLBACK(onSButtonClicked), NULL);
-g_signal_connect(divideButton, "clicked", G_CALLBACK(onDButtonClicked), NULL);
-g_signal_connect(multiplyButton, "clicked", G_CALLBACK(onMButtonClicked), NULL);
-g_signal_connect(clearButton, "clicked", G_CALLBACK(onClearButtonClicked), NULL);
-g_signal_connect(equalButton, "clicked", G_CALLBACK(onEqualButtonClicked), NULL);
-gtk_widget_show(window);
-gtk_main();
}