PTR

PTR is an acronym that can refer to more than one concept in computing and networking. In programming, PTR is commonly used as shorthand for a pointer, a variable that stores a memory address. Pointers enable dynamic memory management and the construction of data structures such as linked lists and trees. In languages like C and C++, pointers can be dereferenced to access the object they point to, and pointer arithmetic can be used to navigate arrays. Pointer usage requires careful handling to avoid errors such as null dereferencing, invalid addresses, and memory leaks. Modern languages and idioms introduce safer or higher-level abstractions, such as references or smart pointers, that manage lifetimes automatically.

In the Domain Name System, PTR refers to a reverse DNS record, a type of DNS record used to map an IP address to a host name. PTR records reside in special in-addr.arpa or ip6.arpa zones and are queried during reverse lookups. They are commonly used in mail server configurations and diagnostic tools, where matching forward and reverse mappings can help verify host identity. The presence and correctness of PTR records can affect deliverability of email and trust in network operations.

Other specialized uses of PTR exist in certain domains, but the two senses above cover the most widely encountered meanings. See also reverse DNS and memory management.