If you're looking at how many resources a particular program takes on your computer or smart phone, you might see discussion of the program's central processing unit usage and how much random access memory, or RAM, it consumes. Other important measurements include how much long-term storage space, such as hard drive space, an application needs. Often a program's rough requirements are spelled out in app stores or on physical software packages so you know if the software will run smoothly on your devices.
CPU vs. Memory
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When a computer program is doing any kind of work, whether it's rendering video for a game or crunching numbers in a spreadsheet, it needs to run a certain number of instructions on the computer's central processing unit.
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The amount of instructions a processor can run per second is measured in megahertz, meaning millions of instructions, or gigahertz, meaning billions of instructions per second. Many modern processors also have multiple cores, meaning subparts that can run different programs and parts of programs in parallel.
Similarly, to run smoothly, most programs need a certain amount of memory to store their working data. This data can be swapped back and forth to a disk, but that takes time and can cause the program to run slowly or even so inefficiently that it's effectively not getting any work done at all.
When you buy a computer or phone, you can research whether its CPU and RAM are sufficient for the programs you run. Similarly, when you buy or download software, you can often see its RAM and processor requirements in the documentation or on the box.
Lower CPU Usage and RAM
If the programs running on your devices are using a lot of the CPU's capacity, this can cause the device to run slowly, run hot and use more power. That's an especially big consideration if you're running on battery power.
If a lot of RAM is in use, programs will generally run more slowly, and it can take longer to switch between programs if you're multitasking.
Not all programs have settings that enable you to adjust your CPU and RAM usage, but some do, particularly games. Check the documentation of the programs you use to see if there are settings you can adjust to get them to conserve resources.
If you're having problems with memory or CPU usage on your devices, you can also close unnecessary programs or parts of programs, such as idle browser tabs. You may want to avoid using other programs while especially demanding software is running.
To understand the CPU usage on your devices, you can use various built-in software. On Windows, use the built-in "Task Manager" program, and on macOS, you can use the similar Activity Monitor. On Linux and Unix systems, a variety of tools are available, including the command-line tool "top."
Other Resource Considerations
CPU and RAM aren't the only resources you'll consider when choosing software and hardware.
Some programs require internet connections of a minimum speed to be useful and many require a minimum amount of drive space to install themselves and the data they work with. Some programs, especially games and video tools, also require graphics cards with a minimum level of specifications to run.
Check your software's requirements and what your hardware can offer to make sure you have the right tools for any computing job.