Changes

The OLPC laptop bucks the trend of "more, faster, fatter"; we aim to provide a computer tailored to the needs of children in the context of their learning, not to the needs of frantic video games or office applications. We are, however, working within constraints of component cost, robustness, and power consumption. To satisfy these constraints, we have opted for NAND flash rather than a harddisk and a modest 128MB of memory (Please see [[Hardware_Specification|hardware specifications]]). Thus developers must make every effort to write efficient code while minimizing memory usage.

The OLPC laptop bucks the trend of "more, faster, fatter"; we aim to provide a computer tailored to the needs of children in the context of their learning, not to the needs of frantic video games or office applications. We are, however, working within constraints of component cost, robustness, and power consumption. To satisfy these constraints, we have opted for NAND flash rather than a harddisk and a modest 128MB of memory (Please see [[Hardware_Specification|hardware specifications]]). Thus developers must make every effort to write efficient code while minimizing memory usage.

Since there is no swap space on the laptop, only a limited number of activities can run concurrently; the Sugar UI exposes these details directly to the user. The [[OLPC Human Interface Guidelines/The Laptop Experience#Home|Home]] screen features an activity ring that contains icons representing each instance of an open [[OLPC Human Interface Guidelines/Activities|activity]]. The size of the ring segment that a given activity occupies represents its overall memory usage; when the ring fills up, no additional activities may be launched until some resources are freed up. Take these limitations into account as you develop activities, since they will have a greater impact on the performance of your software on the laptop than on other platforms.

Since there is no swap space on the laptop, only a limited number of activities can run concurrently; the Sugar UI exposes these details directly to the user. The [[OLPC Human Interface Guidelines/The Laptop Experience/Zoom Metaphor#Home|Home]] screen features an activity ring that contains icons representing each instance of an open [[OLPC Human Interface Guidelines/Activities|activity]]. The size of the ring segment that a given activity occupies represents its overall memory usage; when the ring fills up, no additional activities may be launched until some resources are freed up. Take these limitations into account as you develop activities, since they will have a greater impact on the performance of your software on the laptop than on other platforms.

====Usability====

====Usability====

====Adaptability====

====Adaptability====

There are several variable use conditions that should be taken into consideration in designing activities: the laptop has both a grayscale (sunlight) mode and a color (backlight) mode; the mesh—while always available—may or may not be connected to the Internet at the time the activity is active; the laptop may be configured in either laptop mode (keyboard and touchpad exposed) or [[OLPC Human Interface Guidelines/The Sugar Interface#"Hand-held" Mode|handheld mode]] (game controller, camera, microphone and speakers only). Signal strengths, and therefore bandwidth, may fluctuate, and at times activity partipants may even drop off temporarily. Activities should handle all of these cases with care. E.g., temporary loss of connectivity should be handled silently, and reconnection of an individual to an activity they were previously participating in should happen with no noticeable side-effects as outlined in the guidelines for [[OLPC Human Interface Guidelines/Activities#Activity Robustness|activity robustness]].

There are several variable use conditions that should be taken into consideration in designing activities: the laptop has both a grayscale (sunlight) mode and a color (backlight) mode; the mesh—while always available—may or may not be connected to the Internet at the time the activity is active; the laptop may be configured in either laptop mode (keyboard and touchpad exposed) or [[OLPC Human Interface Guidelines/The Sugar Interface/Input Systems#"Hand-held" Mode|handheld mode]] (game controller, camera, microphone and speakers only). Signal strengths, and therefore bandwidth, may fluctuate, and at times activity partipants may even drop off temporarily. Activities should handle all of these cases with care. E.g., temporary loss of connectivity should be handled silently, and reconnection of an individual to an activity they were previously participating in should happen with no noticeable side-effects as outlined in the guidelines for [[OLPC Human Interface Guidelines/Activities/Activity Basics#Activity Robustness|activity robustness]].

====Recoverability====

====Recoverability====

However, the primary and essential means of recoverability remains the ability to undo one's actions.  Of course, the notion of undo/redo becomes complicated in the realm of collaborative editing, which imposes a limitation on the extent to which undos are possible, since collisions between the things one child wants to undo and the things another child has already changed since they were done occur often.  Nonetheless, we are dedicated to providing this functionality to every extent possible, and [[OLPC Human Interface Guidelines/Activities|activities]] should strive to support this to the best of their ability.

However, the primary and essential means of recoverability remains the ability to undo one's actions.  Of course, the notion of undo/redo becomes complicated in the realm of collaborative editing, which imposes a limitation on the extent to which undos are possible, since collisions between the things one child wants to undo and the things another child has already changed since they were done occur often.  Nonetheless, we are dedicated to providing this functionality to every extent possible, and [[OLPC Human Interface Guidelines/Activities|activities]] should strive to support this to the best of their ability.

(Future revisions of the [[OLPC Human Interface Guidelines/The Sugar Interface#Keyboard|keyboard]] may even have an undo/redo key to further strengthen this idea.)

(Future revisions of the [[OLPC Human Interface Guidelines/The Sugar Interface/Input Systems#Keyboard|keyboard]] may even have an undo/redo key to further strengthen this idea.)

====Interoperability====

====Interoperability====

====Transparency====

====Transparency====

OLPC also hopes to encourage the children using the laptops to explore the the technology under the surface.  Towards this end, a [[OLPC_Human_Interface_Guidelines/The Laptop Experience#View Source|view source]] key has been added to the laptop keyboards, providing them with instant access to the code that enables the activities that they use from day to day.  This key will allow those interested to peel away layers of abstraction, digging deeper into the codebase as they learn.

OLPC also hopes to encourage the children using the laptops to explore the the technology under the surface.  Towards this end, a [[OLPC_Human_Interface_Guidelines/The Laptop Experience/View Source|view source]] key has been added to the laptop keyboards, providing them with instant access to the code that enables the activities that they use from day to day.  This key will allow those interested to peel away layers of abstraction, digging deeper into the codebase as they learn.

To enable such layered exploration, OLPC has written much of what can be in [[Python]], a scripting language, to enable children to view the source code.  This means, aside from general good practice, code should be both readable and well commented.  The [http://www.python.org/dev/peps/pep-0008/ PEP 8] style guidelines for Python provide an excellent resource, and OLPC recommends that developers follow the practices laid out therein unless a compelling reason not to exists.

To enable such layered exploration, OLPC has written much of what can be in [[Python]], a scripting language, to enable children to view the source code.  This means, aside from general good practice, code should be both readable and well commented.  The [http://www.python.org/dev/peps/pep-0008/ PEP 8] style guidelines for Python provide an excellent resource, and OLPC recommends that developers follow the practices laid out therein unless a compelling reason not to exists.