This will be the first in a series of posts on Rust, mostly written from this perspective. Macroĭefines the minimum value for a signed char.ĭefines the maximum value for a signed char.ĭefines the maximum value for an unsigned char.ĭefines the minimum value for type char and its value will be equal to SCHAR_MIN if char represents negative values, otherwise zero.ĭefines the value for type char and its value will be equal to SCHAR_MAX if char represents negative values, otherwise UCHAR_MAX.ĭefines the maximum number of bytes in a multi-byte character.ĭefines the minimum value for a short int.ĭefines the maximum value for a short int.ĭefines the maximum value for an unsigned short int.ĭefines the maximum value for an unsigned int.ĭefines the minimum value for a long int.In the last post I wrote about my journey from Python to Go as my primary language, and how I am now exploring Rust. The following values are implementation-specific and defined with the #define directive, but these values may not be any lower than what is given here. value: This refers to any value assigned to identifierName.Ĭout identifierName: It is the name given to constant.We can use this to declare a constant as shown below: Using #define preprocessor directive: This directive is used to declare an alias name for existing variable or any value.Let us now learn about above two ways in details: In C/C++ program we can define constants in two ways as shown below: Under the signed bit, the range of an int varies from -128 to +127 and under the unsigned bit, int varies from 0 to 255. Now there are various ranges that differ from unsigned to signed bits. The integers that are too big to fit into an int will be taken as long. There can be any types of constants like integer, float, octal, hexadecimal, character constants etc. How can it be constant and vary at the same time? The better name for the second one is a memory constant because they have a "specific storage location in memory".Īs the name suggests the name constants is given to such variables or values in C++ programming language which cannot be modified once they are defined. The second one is called sometimes called constant variable but that name is contradictory all by itself. There are two ways to create symbolic or named constants:Ĭalled a defined constant, we have discussed this concept when we talked about preprocessor directives in Lesson 1, because it uses a textual substitution method controlled by the compiler pre-processor command word "define". Another rule about using ALL CAPS FOR CONSTANTS is an industry rule. One of the rules says those names should be meaningful. Within C++ identifier names have some rules. Let's say it backwards the identifier name is the symbol that represents the data item. A symbolic constant is represented by a name similar to how we name variables. Most text books refer to either symbolic constants or named constants but these two refer to the same concept. Thus, as its name implies – their value can vary.Ĭonstants are used in two ways within C++. Thus, as its name implies – their value is constant.Ī variable is a data item whose value can change during the program's execution. Let's see if we can clear it up.Ī constant is a data item whose value cannot change during the program's execution. Added to the complexity are the explanations from various industry professionals will vary greatly. Various textbooks describe constants using different terminology.
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