Htop is an interactive system-monitor

System monitor

A system monitor is a hardware- or software- based system used to monitor resources and performance in a computer system.Software monitors occur more commonly, sometimes as a part of a widget engine. These monitoring systems are often used to keep track of system resources, such as CPU usage and...

 process-viewer written for Linux. It is designed to replace the Unix program top

Top (Unix)

top is a program found in many Unix-like operating systems. It produces an ordered list of running processes selected by user-specified criteria, and updates it periodically. Default ordering by CPU usage, and only the top CPU consumers shown top shows how much processing power and memory are...

. It shows a frequently updated list of the processes running on a computer, normally ordered by the amount of CPU usage. Unlike 'top', Htop provides a full list of processes running, instead of the top resource-consuming processes. Htop uses color and gives visual information about processor

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

, swap and memory status.

Users often deploy htop in cases where Unix top does not provide enough information about the systems processes, for example when trying to find minor memory leak

Memory leak

A memory leak, in computer science , occurs when a computer program consumes memory but is unable to release it back to the operating system. In object-oriented programming, a memory leak happens when an object is stored in memory but cannot be accessed by the running code...

s in applications. Compared to top, it provides a more convenient, cursor-controlled interface for killing processes.

Htop is written in the C programming language

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

 using the ncurses

Ncurses

ncurses is a programming library that provides an API which allows the programmer to write text user interfaces in a terminal-independent manner. It is a toolkit for developing "GUI-like" application software that runs under a terminal emulator...

 library.

It is possible to run htop on FreeBSD, since it can emulate Linux's procfs

Procfs

procfs is a special filesystem in UNIX-like operating systems that presents information about processes and other system information in a hierarchical file-like structure, providing a more convenient and standardized method for dynamically accessing process data held in the kernel than traditional...

.