Due to its simplicity the classical cyclotron has been used very early for applications in sciency, medicine and industry. Higher energies and intensities were achieved through the concepts of the sector focused isochronous cyclotron and the synchro-cyclotron. Besides those the fixed field alternating gradient accelerator (FFA) represents the most general concept among these types of fixed field accelerators, and the latter one is actively studied and developed for future applications. 20 pages, contribution to the CAS - CERN Accelerator School: Introduction to Accelerator Physics. arXiv admin note: text overlap with arXiv:1302.1001