The B-tree is a widely used data structure for file organization, known for its efficiency in retrieval, insertion, and deletion operations. This paper reviews B-trees and their variations, particularly the B+ tree, and discusses their advantages and costs. It also presents a general-purpose access method based on B-trees. The B-tree is a balanced, multiway, external file organization that ensures efficient and versatile performance. It allows for efficient sequential processing of files while maintaining logarithmic cost for find, insert, and delete operations. B-tree schemes guarantee 50% storage utilization, dynamically allocating and releasing space as the file grows or shrinks. Unlike traditional file systems, B-trees do not require massive reorganization even after heavy transaction traffic. Variations of B-trees, such as B* trees and B+ trees, offer additional benefits. B+ trees, for example, store all keys in the leaves, allowing for efficient sequential processing and reducing the number of secondary storage accesses needed for operations. B* trees optimize storage utilization by ensuring nodes are at least 2/3 full, which can speed up searches by reducing the tree's height. The paper also discusses the use of B-trees in multiuser environments, where they must handle concurrent access and ensure data integrity. Locking protocols and other mechanisms are used to manage concurrent access and prevent conflicts. Additionally, the paper explores various implementation techniques, including compression of keys and pointers, which can enhance performance by reducing the number of nodes accessed during operations. These techniques are particularly useful in virtual memory environments, where B-trees can be mapped into one page of the virtual address space. The paper concludes that B-trees are well-suited for a wide range of applications, including database systems and file access methods, due to their efficiency, versatility, and ability to handle both random and sequential processing.The B-tree is a widely used data structure for file organization, known for its efficiency in retrieval, insertion, and deletion operations. This paper reviews B-trees and their variations, particularly the B+ tree, and discusses their advantages and costs. It also presents a general-purpose access method based on B-trees. The B-tree is a balanced, multiway, external file organization that ensures efficient and versatile performance. It allows for efficient sequential processing of files while maintaining logarithmic cost for find, insert, and delete operations. B-tree schemes guarantee 50% storage utilization, dynamically allocating and releasing space as the file grows or shrinks. Unlike traditional file systems, B-trees do not require massive reorganization even after heavy transaction traffic. Variations of B-trees, such as B* trees and B+ trees, offer additional benefits. B+ trees, for example, store all keys in the leaves, allowing for efficient sequential processing and reducing the number of secondary storage accesses needed for operations. B* trees optimize storage utilization by ensuring nodes are at least 2/3 full, which can speed up searches by reducing the tree's height. The paper also discusses the use of B-trees in multiuser environments, where they must handle concurrent access and ensure data integrity. Locking protocols and other mechanisms are used to manage concurrent access and prevent conflicts. Additionally, the paper explores various implementation techniques, including compression of keys and pointers, which can enhance performance by reducing the number of nodes accessed during operations. These techniques are particularly useful in virtual memory environments, where B-trees can be mapped into one page of the virtual address space. The paper concludes that B-trees are well-suited for a wide range of applications, including database systems and file access methods, due to their efficiency, versatility, and ability to handle both random and sequential processing.