What is the Difference Between API and System Call

The main difference between API and system call is that API is a set of protocols, routines, and, functions that allow the exchange of data among various applications and devices while a system call is a method that allows a program to request services from the kernel.

An API consists of protocols and functions that define the methods of communication among various components. It can be a web-based system, operating system, database or software library. On the other hand, a system call is a method that allows a program to request services from the operating system’s kernel.

Key Areas Covered

1. What is API
     – Definition, Functionality
2. What is System Call
     – Definition, Functionality
3. What is the Difference Between API and System Call
     – Comparison of Key Differences

Key Terms

API, Kernel, System Call

What is an API

Different devices and applications share data between them. Some of them include online reservations and booking systems. API (Application Programming Interface) helps to establish connectivity among devices and applications. Moreover, it is an interface that takes the requests from the user and informs the system about what should be done and return the response back to the user.

For example, assume an online travel service that aggregates information from multiple airlines. The travel service interacts with the airline’s API. The API takes the requests to book seats and select meals from the travel service to the airline system. Then it delivers the airlines responses back to the online travel service and the travel service displays the details to the users. This is a real-world application for an API.

What is a System Call

A computer operates in two modes: user mode and kernel mode. The execution of a program is in the user mode. When the program requires RAM or a hardware resource, it sends a request to the kernel and the mode changes from user mode to kernel mode. System calls refer to these requests. After completing the task, the mode changes back to the user mode. Likewise, the mode changes continuously. This transition is also called context switching.

There are various types of system calls. Some of them are as follows.

Process control system calls – Create, execute, terminate processes, set process attributes, etc.

File management system calls – Create, read, write, delete files, open and close files, set file attributes, etc.

Device management system calls – Request and release devices, set device attributes, etc.

Information management system calls – Get and set system data, get and set time and date, etc.

Communication system calls – Send and receive messages, transfer status information, create and delete communication connections, etc.

Difference Between API and System Call

Definition

An API is a set of protocols, routines, functions that programmers use to develop software to facilitate interaction between distinct systems. In contrast, a system call is a programmatic way in which a computer program requests a service from the kernel of the operating system it is executing on. Thus, these definitions contain the main difference between API and system call.

Usage

Another difference between API and system call  is their usage. An API helps to exchange data between various systems, devices and applications while a system call allows a program to access services from the kernel of the operating system. 

Conclusion

The main difference between API and system call is that API is a set of protocols, routines, functions that allow exchanging data among various applications and devices while a system call is a method that allows a program to request services from the kernel.

Reference:

1. What Is an API?, MuleSoft Videos, 19 June 2015, Available here.
2. “Application Programming Interface.” Wikipedia, Wikimedia Foundation, 16 Nov. 2018, Available here.
3. Explanation-System Calls and System Call Types in Operating System, Last Moment Learning, 12 July 2017, Available here.

Image Courtesy:

1. “Open-APIs-v5” By Camwilliams96 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “System call interface” By system call interface – (CC BY-SA 4.0) via Commons Wikimedia