Completing tasks
- C course
- Beginner
- Lesson 86/116
- 6 min
Learn to update task status with CompleteTask.
The complete_task function
To mark a task as completed we write the complete_task function. It sets the done field of the task to 1.
void complete_task(struct Task tasks[], int id) {
tasks[id - 1].done = 1;
}We use id - 1 because ids start at 1 but array indices start at 0. So we convert the 1-based id into a 0-based index.
1-based id, 0-based index
Task ids start at 1 (the first task has id 1). But C arrays start at 0. So we write tasks[id - 1] to convert the 1-based id into a 0-based index.
complete_task(tasks, 1); /* tasks[0].done = 1 */
complete_task(tasks, 2); /* tasks[1].done = 1 */This split reconciles user-friendly ids with array access. The user types 1, the program uses 0-based.
Practice Add the complete_task function
Add the void complete_task(struct Task tasks[], int id) function to the code below. Inside it write tasks[id - 1].done = 1;. In main add a complete_task(tasks, 1); call before the list_tasks call (to complete the first task). Output should be 1 Shopping 1 and 2 Sport 0.
Starter code
#include <stdio.h>
#include <string.h>
struct Task {
int id;
char title[50];
int done;
};
int add_task(struct Task tasks[], int count, const char *title) {
tasks[count].id = count + 1;
strcpy(tasks[count].title, title);
tasks[count].done = 0;
return count + 1;
}
void list_tasks(struct Task tasks[], int count) {
for (int i = 0; i < count; i++) {
printf("%d %s %d\n", tasks[i].id, tasks[i].title, tasks[i].done);
}
}
int main(void) {
struct Task tasks[10];
int count = 0;
count = add_task(tasks, count, "Shopping");
count = add_task(tasks, count, "Sport");
list_tasks(tasks, count);
return 0;
}Sample solution
#include <stdio.h>
#include <string.h>
struct Task {
int id;
char title[50];
int done;
};
int add_task(struct Task tasks[], int count, const char *title) {
tasks[count].id = count + 1;
strcpy(tasks[count].title, title);
tasks[count].done = 0;
return count + 1;
}
void list_tasks(struct Task tasks[], int count) {
for (int i = 0; i < count; i++) {
printf("%d %s %d\n", tasks[i].id, tasks[i].title, tasks[i].done);
}
}
void complete_task(struct Task tasks[], int id) {
tasks[id - 1].done = 1;
}
int main(void) {
struct Task tasks[10];
int count = 0;
count = add_task(tasks, count, "Shopping");
count = add_task(tasks, count, "Sport");
complete_task(tasks, 1);
list_tasks(tasks, count);
return 0;
}Expected output
1 Shopping 1 2 Sport 0
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match completion concepts
| Term | Meaning |
|---|---|
done = 1 |
completed |
done = 0 |
pending |
id - 1 |
array index |
tasks[i] |
task array |
2 How do you mark a task as completed?
- tasks[i].id = 1
- tasks[i].title = "done"
- tasks[i].done = 1 Correct answer
- tasks[i] = NULL
Explanation: Setting the done field to 1 marks the task as completed.
3 Mark as done
tasks[id].____; /* mark task as completed */tasks[id].done = 1; /* mark task as completed */Explanation: done = 1 marks the task as completed.