iMacs are a range of all-in-one Macintosh desktop computers designed and built by Apple Inc. It has been the main part of Apple's consumer desktop contributions since its introduction in 1998, and has evolved through six distinct forms.
In its original form, the iMac G3 had a gum-drop or egg-shaped look, with a CRT monitor(Cothode Ray Tube monitor), mainly surrounded by a colored, translucent plastic case, which was paused early on with a sleeker design notable for its slot-loaded optical drive. The second major revision, the iMac G4, moved the design to a crescent base containing all the main components and an LCD monitor(Liquid-Crystal Dysplay) on a freely moving arm attached to it. The third and fourth major modifications, the iMac G5 and the Intel iMac individually, placed all the components immediately behind the display, creating a slim, unified design (Unibody) that tilts only up and down on a simple metal base. The fifth major upgrade shared the same form as the previous model, but was thinner and used anodized aluminum and a glass panel over the entire front. The newest iMac uses a different display unit, omits the SuperDrive, and uses different production techniques from the older unibody versions. This allows it to be thinner than older models, with an edge thickness of 5.5mm. It also includes a dual microphone setup, and includes SSD or HDD storage, or an Apple Fusion Drive, a hybrid of solid state and hard disk drives. The latest model was announced on October 23, 2012, with the 21.5" version released on November 30 and the 27" version released in December; these were refreshed on September 24, 2013, with new Haswell processors, faster graphics, faster and larger SSD options and 802.11ac WiFi cards.