A cache structure includes data arrays and at least one tag array configured to point to lines of data in a plurality of the data arrays. In one example, a control device of the inkjet recording apparatus may stop conveyance on the sheet depending on the image to be formed in one or more portions of the sheet. According to the present invention constructed as above, since the hooks of the latch for engaging the display and the main body in a portable computer with relatively large dimensions may be installed at both ends of the display, the latch makes the engagement between the display and the main body secure, and a space necessary to install the latch in the display can also be minimized. The length may be reduced or extended at both front end and aft end if needed. The variable aperture assembly provides f-number matching by adjusting the infrared radiation admitting opening to the size necessary to effectively match the numerous f-numbers of the optics, or by adjusting to a size so that a fixed aperture on the radiation shield becomes the effective aperture stop, providing the f-number matching. There is a downhole valve disposed within the fluid chamber, the downhole valve having a second seating surface engageable with a downhole facing sealing shoulder in the fluid chamber.