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Learn to use hash tables with online courses and programs

Hash tables can be useful for data storage in various contexts. They store key values, perform indices, and can enhance efficiency when working with data. Practice using hash tables with online courses delivered through edX.
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What is a hash table? 

A hash table (sometimes called a “hash map”) is a data structure that maps keys to corresponding values, like a dictionary. They are used to look up information quickly, regardless of how much data is stored in the table. The action performed is called a “hashing function”. When you look up a person’s name in your phone’s address book, a hashing function searches through the device memory until it locates their information. In this case, the person’s name is the key and their phone number, address, and other data are the values. 

Hash tables can help speed up a variety of tasks across many different industries. Learning how to use them can benefit individuals who aspire to start a career in fields such as:Footnote 1

  • Cybersecurity: Hashing can help to add an extra layer of security when encrypting user passwords. It can also be used in the detection of malicious activities as a function of antivirus software.

  • Data analytics: Professionals who work with data can use hash tables to quickly and easily look up information. They may also use hashing for data compression.

  • Network management: User requests can be sent through a hashing function to distribute them to various servers and avoid overload. 

There are many other uses for hash tables, such as preventing discrepancies in digital signatures, protecting files from tampering, and reducing duplicate files in a network.Footnote 2 Because of their wide array of applications, hash tables can be a useful tool for anyone who plans to work with data.

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Hash table tutorial curriculum

If you’re pursuing an education in computer science, coding, or a similar subject, you may find that hash tables are included in your coursework. You may first focus on the basics of what hash tables are and how they work, learning how to store data in a table and use a hashing function to retrieve it. And you may practice how to apply this knowledge to a project or problem related to your topic of study.

Topics covered in classes that teach you about hash tables can include:

  • How to implement hash tables and similar data structures

  • How to store and modify the objects on a hash table

  • How to use different hash functions

  • What types of hash table implementation are best suited to particular tasks

  • How to troubleshoot using hash tables

  • How to implement the rehashing process

  • How to create and use distributed key-value storage systems

  • How to conduct pattern searches

edX offers a variety of learning opportunities focused on many different subjects. From individual courses to full degree programs that can enable you to earn a bachelor’s in computer science or pursue a master’s in data science, there are many options for learners to expand their knowledge of different fields. Begin learning with edX today. 

Explore jobs that use hash tables 

Professionals in many different industries rely on hash tables to complete important tasks. Cybersecurity professionals use hashing functions to securely store passwords and other sensitive information.Footnote 3 The pharmaceutical engineering industry uses hash tables to encrypt the transfer of patient information on a blockchain.Footnote 4 The fintech industry also relies on blockchain technology to ensure the security of digital transactions. This is especially important when working with cryptocurrency, which is mined through hashing to link blocks of a distributed ledger.Footnote 5

If you’re interested in better understanding how to apply hash tables to your existing career, consider expanding your technical skill set by enrolling in online learning. The roles outlined above can have varying skills and educational requirements with some employers preferring that job candidates hold a bachelor’s degree or even a master’s degree. However, you can also build your knowledge with specialized boot camps. With edX, you can find the right educational pathway that aligns with your professional development goals and career aspirations. 

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Frequently asked questions

A hash table is a compact data structure that stores one or more key/value pairs. It is used to store data and to make it accessible to users. A hash table can solve an algorithmic challenge, cache data for fast access, or index a database.

Data in a hash table is stored in an array format. This means each data value has its unique index value. So long as you have the index for the table, data retrieval is faster when compared to other data structures with similar levels of sophistication.

A hash function maps numeric or alphanumeric data keys to an integer value or index, which falls into the hash table. It represents a character string but is typically smaller than that string and can be used to generate indices, as well as to compress or encrypt data. This is particularly useful in database indexing as it is easier to search for the hash value than the entire character string.

A hash collision occurs when a hash function generates the same index for multiple keys. This causes a conflict because only one value should be stored for each index bucket, and each bucket should have a unique value.

Hash table implementation should be considered whenever constant lookup time and insertion of database values is required. It is also suitable for cryptographic applications, where the hash can be substituted for the actual character string. The result can only be decrypted by someone who possesses or manages to recreate the index. A hash table is also useful for indexing data, since the hash is generally smaller and easier to handle than the data it represents.Footnote 6

MD5, SHA-2, and CRC32 can be used for file integrity checks. The MD5 message-digest algorithm can be used to verify data integrity. The United States National Security Agency designed the SHA-2 (Secure Hash Algorithm 2) for cryptographic purposes. The CRC32 is a variant of the Cyclic Redundancy Check used to detect accidental changes to data.Footnote 7