iMode - Using cHTML

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In consideration of the inherently limited bandwidth of the cellular network, i-Mode employs Compact HTML (C-HTML), a simplified version of HTML similar to Wireless Markup Language (WML) used in WAP networks and as well as DoCoMo proprietary protocols ALP (HTTP) and TLP (TCP, UDP).

I-mode-compatible HTML websites are easy to navigate since all basic operations can be performed using a combination of four buttons, cursor forward, cursor backward, select, and back (return to previous page).

There are functions that require two-dimensional navigation such as image maps and functions that require more intensive processing such as frames and tables are not included in the standard i-Mode HTML specifications.

i-Mode-compatible HTML provides extended tags for special use on cell phones such as the 'tel:' tag, which is used to hyperlink a telephone number and let users initiate a call by clicking on a link.

Following major features of HTML have not been included in i-Mode compatible HTML, i.e., cHTML:

  • Background colours and images

  • Frames

  • Image maps

  • JPEG images

  • Multiple character fonts and styles

  • Style sheets

  • Tables

cHTML compliance hardware includes:

  • Small memory : 128-512Kbytes RAM, and 512K-1Mbytes ROM.

  • Low power CPU : 1-10 MIPS class CPU for embedded systems.

  • Small display : 50x30 dots, 100x72 dots, and 150x100 dots.

  • Restricted colors : mono-color (black and white).

  • Restricted character fonts :only single font.

  • Restricted input method : several control buttons and number buttons (0-9).

i-Mode supports 256 color GIF files. In addition, only images in GIF 87, 87a, and 89a formats can be used. The maximum size of a GIF image should be 94 x 72 dots.

The World Wide Web Consortium (www.w3.org) contains a complete listing of the cHTML tags available to developers. Also, you can visit the NTT DoCoMo site at www.nttdocomo/ser2.htm for an outline of cHTML tags available to developers.

There are millions of HTML-based content resources, various software tools, and public materials, which can be used to develop i-Mode applications.



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