Pascal case -- or PascalCase -- is a programming naming convention where the first letter of each compound word in a variable is capitalized.
The use of descriptive variable names is a software development best practice. However, modern programming languages do not allow variables names to include blank spaces.
Pascal case naming convention
When more than one word is needed to properly convey a variable's purpose, the PascalCase naming convention dictates that words be appended to each other. The use of a single uppercase letter for each additional word makes it easier to read code and discern the purpose of variables.
The term Pascal case was popularized by the Pascal programming language. Pascal itself is case insensitive, so the use of PascalCase was not a requirement. However, it became standard convention for Pascal developers, as it improved the readability of code.
Pascal case examples
The following are examples of terms written in Pascal case:
Synonyms for Pascal case include medical case, upper camel case, studly caps, inter-caps and humpy case.
Pascal case vs. camel case
Pascal case requires that the first letter of a variable be in upper case. In contrast, camel case -- also known as CamelCase -- allows the first letter to be either upper or lower case. To clarify between the two options, the terms UpperCamelCase and lowerCamelCase are often used. Pascal case would be equivalent to UpperCamelCase.
Pascal vs. snake vs. kebab case
Two popular alternatives to Pascal case are snake case and kebab case. Snake case separates words with an underscore, while kebab case uses a dash:
Pascal case in Java
In Java, all classes, interfaces and enums are expected to use Pascal case. Variables in Java are to be written in lowerCamelCase, and static variables are in snake case.
Pascal case naming convention problems
Acronyms and abbreviations can present a challenge for developers who use the PascalCase naming convention. For example, if a developer was to use the NASA images APIs, the following two variable names would comply with Pascal case naming standards:
The latter is arguably easier to read. However, the former respects the official NASA trademark.
In addition, the manner in which the term URL is written is a prime example of an inconsistent application of PascalCase throughout the industry. For example, Java network APIs always reference the term URL in all caps, as with the classes URLConnection and URLEncoder. In contrast, the Spring APIs include classes such as UrlResource and UrlTag.
The inconsistent application of any naming convention may result in software defects that are difficult to diagnose. As such, it is important for programming teams to decide how to apply naming conventions for the various corner cases that arise in the software development lifecycle.