# U

- [Ulam numbers](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/ulam_numbers.md)
- [Ulam spiral for primes](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/ulam_spiral_for_primes.md)
- [Ultra useful primes](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/ultra_useful_primes.md)
- [Unbias a random generator](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unbias_a_random_generator.md)
- [Undefined values](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/undefined_values.md)
- [Unicode strings](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unicode_strings.md)
- [Unicode variable names](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unicode_variable_names.md)
- [Universal Turing machine](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/universal_turing_machine.md)
- [Unix](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unix.md)
- [Ls](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unix/ls.md)
- [Unprimeable numbers](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/unprimeable_numbers.md)
- [URL decoding](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/url_decoding.md)
- [URL encoding](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/url_encoding.md)
- [User input](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/user-input.md)
- [Graphical](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/user-input/graphical.md)
- [Text](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/user-input/text.md)
- [UTF-8 encode and decode](https://trizen.gitbook.io/sidef-lang/programming_tasks/u/utf-8_encode_and_decode.md)