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A single 0 or 1 is referred to as a bit.
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mem(7d) [sunos man page]

mem(7D) 							      Devices								   mem(7D)

NAME
mem, kmem, allkmem - physical or virtual memory access SYNOPSIS
/dev/mem /dev/kmem /dev/allkmem DESCRIPTION
The file /dev/mem is a special file that provides access to the physical memory of the computer. The file /dev/kmem is a special file that provides access to the virtual address space of the operating system kernel, excluding memory that is associated with an I/O device. The file /dev/allkmem is a special file that provides access to the virtual address space of the operating system kernel, including memory that is associated with an I/O device. You can use any of these devices to examine and modify the system. Byte addresses in /dev/mem are interpreted as physical memory addresses. Byte addresses in /dev/kmem and /dev/allkmem are interpreted as kernel virtual memory addresses. A reference to a non-existent location returns an error. See ERRORS for more information. The file /dev/mem accesses physical memory; the size of the file is equal to the amount of physical memory in the computer. This size may be larger than 4GB on a system running the 32-bit operating environment. In this case, you can access memory beyond 4GB using a series of read(2) and write(2) calls, a pread64() or pwrite64() call, or a combination of llseek(2) and read(2) or write(2). ERRORS
EFAULT Occurs when trying to write(2) a read-only location (allkmem), read(2) a write-only location (allkmem), or read(2) or write(2) a non-existent or unimplemented location (mem, kmem, allkmem). EIO Occurs when trying to read(2) or write(2) a memory location that is associated with an I/O device using the /dev/kmem spe- cial file. ENXIO Results from attempting to mmap(2) a non-existent physical (mem) or virtual (kmem, allkmem) memory address. FILES
/dev/mem Provides access to the computer's physical memory. /dev/kmem Provides access to the virtual address space of the operating system kernel, excluding memory that is associated with an I/O device. /dev/allkmem Provides access to the virtual address space of the operating system kernel, including memory that is associated with an I/O device. SEE ALSO
llseek(2), mmap(2), read(2), write(2) WARNINGS
Using these devices to modify (that is, write to) the address space of a live running operating system or to modify the state of a hardware device is extremely dangerous and may result in a system panic if kernel data structures are damaged or if device state is changed. SunOS 5.10 18 Feb 2002 mem(7D)

Check Out this Related Man Page

MEM(4)                                                       Linux Programmer's Manual                                                      MEM(4)

NAME
mem, kmem, port - system memory, kernel memory and system ports DESCRIPTION
/dev/mem is a character device file that is an image of the main memory of the computer. It may be used, for example, to examine (and even patch) the system. Byte addresses in /dev/mem are interpreted as physical memory addresses. References to nonexistent locations cause errors to be returned. Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present. Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which can be accessed through this file. For example: on x86, RAM access is not allowed but accessing memory-mapped PCI regions is. It is typically created by: mknod -m 660 /dev/mem c 1 1 chown root:kmem /dev/mem The file /dev/kmem is the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed. Since Linux 2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled. It is typically created by: mknod -m 640 /dev/kmem c 1 2 chown root:kmem /dev/kmem /dev/port is similar to /dev/mem, but the I/O ports are accessed. It is typically created by: mknod -m 660 /dev/port c 1 4 chown root:kmem /dev/port FILES
/dev/mem /dev/kmem /dev/port SEE ALSO
chown(1), mknod(1), ioperm(2) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. Linux 2015-01-02 MEM(4)

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