Some data in the kernel, despite not being represented by an opaque type, requires a specific data type. Two examples are jiffy counts and the flags parameter used in interrupt control, both of which should always be stored in an unsigned long. When storing and manipulating specific data, always pay careful attention to the data type that represents the type and use it.
It is a common mistake to store one of these values in another type, such as unsigned int. Although this will not result in a problem on bit architectures, bit machines will have trouble. Often, as a programmer, you need explicitly sized data in your code. This is usually to match an external requirement, such as with hardware, networking, or binary files.
For example, a sound card might have a bit register, a networking packet might have a bit field, or an executable file might have an 8-bit cookie. In these cases, the data type that represents the data needs to be exactly the right size. Table Explicitly-Sized Data Types Type. These explicit types are merely typedefs to standard C types.
On a bit machine, they may look like this:. These types can be used only inside the kernel, in code that is never revealed to user-space say, inside a user-visible structure in a header file. This is for reasons of namespace. The kernel also defines user-visible variants of these types, which are simply the same type prefixed by two underscores. This type is the same as u32 ; the only difference is the name. You can use either name inside the kernel, but if the type is user-visible you must use the underscored prefixed version to prevent polluting user-space's namespace.
The C standard says that the char data type can be either signed or unsigned. It is the responsibility of the compiler, the processor, or both to decide what the suitable default for the char type is. On most architectures, char is signed by default and thus has a range from to On a few other architectures, such as ARM, char is unsigned by default and has a range from 0 to For example, on systems where a char is by default unsigned, this code ends up storing instead of 1 in i :.
On other machines, where char is by default signed, this code correctly stores 1 in i. Es igual a megabits, kilobits , o bits Gigabyte es una unidad de almacenamiento de datos digitales. Es igual a megabytes, kilobytes o bytes. Equivale a 2 10 bytes. Es igual a bits. Es igual a kilobits o bits. Megabyte es una unidad de almacenamiento de datos digitales. Es igual a kilobytes o 1,, bytes. Es igual a terabits, gigabits, megabits. Petabyte es una unidad de almacenamiento de datos digitales.
Es igual a 1. Es igual a gigabytes, 1. Terabyte es una unidad de almacenamiento de datos digitales. Es igual a gigabytes, megabytes , kilobytes. Il est l'acronyme de chiffres binaires. Sa taille peut varier en fonction de la machine ou le langage informatique.
Byte ist eine Informationseinheit in der Computertechnik eingesetzt. Er bezieht sich auf eine Einheit der adressierbaren Speicher. Es ist gleich Megabit, Kilobit oder Bit. Gigabyte ist eine Einheit der digitalen Datenspeicherung. Es ist gleich Megabyte, Kilobyte oder byte. Die Einheit ist Symbol der kibibyte KiB. Es ist gleich Bit. Es ist gleich Kilobit oder Bit. Megabyte ist eine Einheit der digitalen Datenspeicherung.
Es ist gleich Kilobyte oder Byte. Es ist gleich Terabit, Gigabit, Megabit. Petabyte ist eine Einheit der digitalen Datenspeicherung. Es ist gleich Terabyte, Gigabyte Megabyte. Die Einheit ist Symbol der tebibyte TiB. Es ist gleich Gigabits, Megabit, Kilobit. Terabyte ist eine Einheit der digitalen Datenspeicherung. Es ist gleich Gigabyte, Megabyte Kilobyte. Toggle navigation Extra Conversion. Density Energy Force Frequency. Power Pressure Speed Time. Connect and share knowledge within a single location that is structured and easy to search.
A byte is 8 bits side by side. A word is 2 bytes side by side. A double word is 2 words side by side. A quad word is 2 double words side by side. For convenience, 8 bits are usually grouped into a single block, conventionally called a byte. The next-largest named block of bits is a word. The definition and size of a word are not absolute, but vary from computer to computer. A word is the size of the most convenient block of data for the computer to deal with.
So is a word 2 bytes 16 bits , or is it the most convenient block of data for the computer to deal with? I am also not sure what this means..
I'm not familiar with either of these books, but the second is closer to current reality. The first may be discussing a specific processor. The and processors used 16 bit words, and it's likely this is the machine the first author was writing about.
In the 50's and 60's there were machines with words sizes that seem quite strange to us now, such as 4, 9 and Since about the 70's word size has commonly been a power of 2 and a multiple of 8. The second quote is correct, the size of a word varies from computer to computer. The ARM NEON architecture is an example of an architecture with bit words, where bit quantities are referred to as "doublewords" and bit quantities are referred to as "quadwords":.
A NEON operand can be a vector or a scalar. A NEON vector can be a bit doubleword vector or a bit quadword vector. A "bit" is a binary digit, either a 1 or 0. A series of binary numbers is called a "word". In addition to the other answers, a further example of the variability of word size from one system to the next is in the paper Smashing The Stack For Fun And Profit by Aleph One:.
We must remember that memory can only be addressed in multiples of the word size. A word in our case is 4 bytes, or 32 bits. So our 5 byte buffer is really going to take 8 bytes 2 words of memory, and our 10 byte buffer is going to take 12 bytes 3 words of memory. This is how the OS translates your keyboard key strokes into letters on the screen. When you press the ' A ' key, the keyboard sends a binary signal equal to the number 97 to the computer, and the computer prints a lowercase ' a ' on the screen.
If you replace '97' with any number from 0 to , you will see the character associated with that number on the system's character code page printed on the screen.
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