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In Programming, What Is a Semaphore?

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  • Written By: Troy Holmes
  • Edited By: W. Everett
  • Last Modified Date: 07 October 2014
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In computer programming a semaphore is a signaling technique that uses special variables within a computer programming language. This signal is used to represent counters, and true-false statements. The use of semaphores has been adopted by most software languages. It is more prevalent within object oriented programming including Java®, C#, and Smalltalk®.

Semaphores have been used in computer programming for several decades. These techniques are typically implemented in low-level software code. This is typically used as a synchronization technique to manage triggers and events within an application. The semaphore variable is monitored for changes, which signals a change in process within the application.

Creating a semaphore within a program makes the software more intuitive. This coding style is considered a best practice by software developers because it makes the code easier to maintain. The use of Boolean variables within a software program enables better logical flow. This can be used in a flow loop to enable a process to continue until the Boolean flag becomes changed.

Computer programming is a highly complex logical flow of data and process steps. This coding effort requires the use of flags and counter devices to manage the logic flow of the processes within the program. Using a semaphore is a good practice because it makes the code easier to read.

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A timer is an example of a semaphore within a software program. Most timer routines are required to complete business steps based on scheduled tasks. The timer routine checks the internal clock of the computer system to determine when to start and stop. This is similar to an alarm clock set to go off at a particular time. The timer process remains dormant until the computer clock reaches the predefined setting.

Many computer programs require counter processes. This is a logic flow that must complete a specified number or iterations before completion. A semaphore is typically used within a counter routine to represent to number of iterations required. The program will exit the flow loop once the counter matches the predefined iteration setting.

Semaphores are typically used within the internal processes of computer operating systems. These low-level processes are necessary to ensure the computer can manage multiple tasks. The use of flags and counter logic is more prevalent in the operating system because it is responsible for coordinating complex tasks for multiple programs within the computer.

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