Can we get address of register variable in C?
Table of Contents
- 1 Can we get address of register variable in C?
- 2 Does register have address?
- 3 When should register modifier be used?
- 4 Can we declare register variable as global?
- 5 What is register addressing?
- 6 Which is not a valid C variable name?
- 7 How to take the address of a variable with register storage?
- 8 Why don’t C++ compilers use the register keyword?
Can we get address of register variable in C?
Register variables tell the compiler to store the variable in CPU register instead of memory. We can never get the addresses of these variables. …
Why is address of register variable not accessible?
1) If you use & operator with a register variable then compiler may give an error or warning (depending upon the compiler you are using), because when we say a variable is a register, it may be stored in a register instead of memory and accessing address of a register is invalid.
Does register have address?
Registers do have addresses, even though they don’t generally reside in memory. Think about it a minute : an address denotes a location in some space, where memory is just one instance of a space.
Which of the following is not possible in a register variable?
Discussion Forum
| Que. | Which of the following operation is not possible in a register variable? |
|---|---|
| b. | Copy the value from a memory variable |
| c. | Global declaration of register variable |
| d. | All of the mentioned |
| Answer:All of the mentioned |
When should register modifier be used?
When should the register modifier be used? Does it really help? The register modifier hints to the compiler that the variable will be heavily used and should be kept in the CPU’s registers, if possible, so that it can be accessed faster.
Can we declare register variable as global in C?
Registers can only be reserved for variables of pointer type. A global register variable cannot be initialized. The register dedicated for a global register variable should not be a volatile register, or the value stored into the global variable might not be preserved across a function call.
Can we declare register variable as global?
You can define a global register variable and associate it with a specified register like this: register int *foo asm (“r12”); Note that this is the same syntax used for defining local register variables, but for a global variable the declaration appears outside a function.
How does address register work?
In a computer, the memory address register (MAR) is the CPU register that either stores the memory address from which data will be fetched to the CPU, or the address to which data will be sent and stored. MAR holds the memory location of data that needs to be accessed.
What is register addressing?
Register mode: In register addressing the operand is placed in one of 8 bit or 16 bit general purpose registers. The data is in the register that is specified by the instruction. Here one register reference is required to access the data. Example: MOV AX,CX (move the contents of CX register to AX register)
Where do register variables reside?
Discussion Forum
| Que. | Register variables reside in |
|---|---|
| b. | registers |
| c. | heap |
| d. | main memory |
| Answer:registers |
Which is not a valid C variable name?
Option (C) 123var is not a valid C variable name. Explanation: For naming a C variable, capital letters, small letters, underscore, and even numbers can be used. However, the variable name cannot start with numbers and hence, 123var is incorrect.
Which operator Cannot be used with register variable?
In C programming language we are not allowed to use address-of operator(&) with variables which are declared with register storage class specifier. But if we make a c++ program and perform the same task (i.e use the & with register storage variable) it doesn’t gives us any error. eg.
How to take the address of a variable with register storage?
In C, you cannot take the address of a variable with register storage. Cf. C11 6.7.1/6: A declaration of an identifier for an object with storage-class specifier register suggests that access to the object be as fast as possible. The extent to which such suggestions are effective is implementation-defined.
What is the difference between Register in C and C++?
C and C++ are different languages. In C, you cannot take the address of a variable with register storage. In C++, register is a deprecated, meaningless keyword that has no effect (except perhaps serve as a compiler hint), and variables declared as register still just have automatic storage.
Why don’t C++ compilers use the register keyword?
C compilers are also free to ignore the register keyword other than to enforce the restriction that you can’t take the variable’s address. Since register no longer requires that a variable occupies a register (it’s been decades since it did), it’s a completely pointless restriction, which is why C++ dropped it.
What is a registerspecifier in C++?
A registerspecifier is a hint to the implementation that the variable so declared will be heavily used. [ Note: The hint can be ignored and in most implementations it will be ignored if the address of the variable is taken.
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