Summary 2023-2024 Jelke de Haan
INFOB1IMM | Computerdenken
Chapter 1: What’s in a Computer?
We can look at a computer from at least two viewpoints:
1. The logical or functional organization: what are the pieces, what do they do and how are they
connected?
2. The physical structure: what the pieces look like and how they are built.
The physical properties change at an amazing rate, as does how fast it runs, but the functional behavior
is quite stable.
There are different kind of computers who are all fundamentally similar even though they look very
different: laptop, desktop computer, Apple Macintosh, Chromebook, smartphones, tablets, e-book
readers. Today’s computers are much smaller, cheaper, faster and more reliable than the ones from 50
years ago.
The debates PCs versus Macs and Apple phones versus Android phones goes on, but it raises some
good questions and helps to get people thinking about what is different between different kinds of
computing devices an what is really the same. People have good reasons – functional, economic,
esthetic – for choosing one kind over others but underneath the hardware that does the computing
is very similar. The choice is often made because of the network effect: the more other people use
something, the more useful it will be for you, roughly in proportion to how many others there are.
1.1 Logical Construction
An abstract picture of what’s in a simple generic computer looks like the next figure: a processor (the
CPU), some primary memory (RAM), some secondary storage (a disk) and a variety of other
components, all connected by a set of wires called a bus that transmits information between them.
The basic organization has been standard since the 1940s. It’s often called the von Neumann
architecture, after John van Neumann, who described it in a 1946 paper. Translated into today’s
terminology, the CPU provides arithmetic and control, the RAM and disk are memory storage, and the
keyboard, mouse and display interact with the human operator.
1.1.1 CPU
The processor or central processing unit (CPU) is the brain. The CPU does arithmetic, moves data
around, and controls the operation of the other components. It has some basic operations that it can
perform but it does so very fast, billions per second. It can decide what operations to perform next
based on the results of previous computations.
, Summary 2023-2024 Jelke de Haan
When buying a computer, the CPU is often described in very difficult terms. What does “2.2 GHz dual-
core Intel Core i7 processor” mean? Intel makes the CPU, “Core i7” is just a marketing term. This
particular processor has two processing units in a single package: “core” has become a synonym for
“processor”. It is, however, sufficient to think of the combination as the CPU, no matter how many
cores it has. “2.2 GHz” is the interesting part. CPU speed is measured in terms of the number of
operations or instructions or parts thereof that it can do in a second. It uses an internal clock to step
through its basic operations. One measure of speed is the number of such ticks per second. One tick
per second is called one hertz (Hz), after Heinrich Hertz. Computers today typically run in the billions
of hertz, or gigahertz (GHz), so 2.2 GHz means 2.200.200.000 ticks per second. The human heartbeat
is almost 100.000 beats per day.
1.1.2 RAM
The primary memory or random access memory (RAM) stores information that is in active use by the
processor and other parts of the computer. Its contents can be changed by the CPU. The RAM stores
the data that de CPU is currently working on, and the instructions that tell the CPU what to do with
the data. This is important: by loading different instructions into memory, we can make the CPU do a
different computation. This makes the stored-program computer a general-purpose device.
RAM is called random access because the CPU can access the information stored at any place
within it as quickly as in any other. When you have to run all the data until you get to the data you
need is called sequential access. Most RAM is volatile: its contents disappear if the power is turned
off, and all this currently active information is lost.
Every computer has a fixed amount of RAM. Capacity is measured in bytes, where a byte is an
amount of memory that’s big enough to hold a single character. More RAM usually translates into
faster computing, since there’s never enough for all the programs that want to use it at the same time,
and it takes time to move parts of an unused program out to make room for something new.
1.1.3 Disks and other secondary storage
Secondary storage holds information even when the power is turned off, it’s non-volatile. There are
two main kinds of secondary storage:
1. The magnetic disk, usually called the hard disk or hard drive:
Magnetic disks store information by setting the direction of magnetization of tiny
regions of magnetic material on rotating surfaces. Data is stored in concentric tracks that are
read an written by a sensor that moves from track to track. Disk space is about 100 times
cheaper per byte than RAM, but accessing information is slower. It takes about ten
milliseconds for the disk drive to access any particular track on the surface; data is then
transferred at roughly 100 MB per second.
2. Flash memory, often called solid state disk:
More and more laptops have solid state disks which use flash memory instead of
rotating machinery. Flash memory is non-volatile; information is stored as electric charges in
circuitry that maintains the charge in individual circuit elements without using any power.
Stored charges can be read, erased and overwritten with new values. Flash memory is faster,
lighter, more reliable and requires less power than conventional disk storage. A typical laptop
disk holds perhaps 500 GB and external drives that can be plugged in to a USB socket have
capacities in the multi-terabyte (TB) range.
A disk is a good example of the difference between logical structure and physical implementation.
Hardware in the disk itself and software in the operating system create the organizational structure.
The logical organization is so well matched to people that other devices provide the same organization
even though they use different physical implementation to achieve it. The data on a disk could be
stored on rotating machinery, integrated circuits with no moving parts, or something else entirely. An
idea in computing is abstraction: physical implementation details are hidden.
, Summary 2023-2024 Jelke de Haan
1.1.4 Et cetera
A lot of other devices serve special functions. Mice, keyboards, touch screens, microphones, cameras
and scanners all allow users to provide input. Displays, printers and speakers output to users.
Networking components communicate with other computers. They are not connected by one bus, but
there are multiple buses inside a computer, with properties appropriate to their function. The
Universal Serial Bus (USB) is an example of a bus that makes an appearance outside of the computer
as well.
All of these devices have gone through the same evolution as processors, memory and disks: the
physical properties have changed rapidly, towards more capabilities in a smaller package at a lower
price. They are also converging into a single one; a cell phone consist of many devices (cameras,
watches, etc.). A smartphone has the same abstract architecture as a laptop, though with major
implementation differences due to size and power constraints. Phones don’t have hard disks, but they
do have flash memory to store information when the phone is turned off. The external devices are
mostly only Bluetooth, a socket for headphones, an external microphone and a USB connector.
1.2 Physical Construction
Physical construction barely changes over time. For example, an SD card or a laptop disk from a decade
old are likely to look the same as one from today, but the capacity is much higher and the price is lower.
There’s a clear progression in the circuits boards that hold the components of a computer:
there are fewer components today because more of the circuitry is inside them, the wiring is finer and
the connecting pins are more numerous and much closer together.
Electronic circuits in computers are built from large numbers of a handful of basic elements. The most
important of these is the logic gate, which computes a single output value based on one or two input
values; it uses input signals like voltage or current to control an output signal, also voltage or current.
Given enough of such gates connected in the right way, it’s possible to perform any kind of
computation.
The fundamental circuit element is the transistor. In a computer, a transistor is a device that
can turn a current on or off under the control of a voltage. Logic gates used to be built from discrete-
components (vacuum tubes and individual transistors).
Logic gates are created on integrated circuits (ICs), often called chips or microchips. An IC has
all the components and wiring of an electronic circuit on a single flat surface that is manufactured by
a complex sequence of optical en chemical processes to produce a circuit that has no discrete pieces
and no conventional wires. ICs are much smaller and more robust than discrete-component circuitry.
Chips are fabricated on circular wafers about 30 cm in diameter; they are sliced into separate chips. A
typical chip is mounted in a larger package with pins that connect it to the rest of the system.
Gordon Moore observed in 1965 that as technology improved, the number of transistors that could
be manufactured on an integrated circuit of a particular size was doubling approximately every year, a
rate that he later revised to every two years. This meant that computing power was doubling every
two years, if not faster. This exponential growth, now known as Moore’s Law, has been going on for
over fifty years, so integrated circuits now have well over a million times as many transistors as they
did in 1965.
INFOB1IMM | Computerdenken
Chapter 1: What’s in a Computer?
We can look at a computer from at least two viewpoints:
1. The logical or functional organization: what are the pieces, what do they do and how are they
connected?
2. The physical structure: what the pieces look like and how they are built.
The physical properties change at an amazing rate, as does how fast it runs, but the functional behavior
is quite stable.
There are different kind of computers who are all fundamentally similar even though they look very
different: laptop, desktop computer, Apple Macintosh, Chromebook, smartphones, tablets, e-book
readers. Today’s computers are much smaller, cheaper, faster and more reliable than the ones from 50
years ago.
The debates PCs versus Macs and Apple phones versus Android phones goes on, but it raises some
good questions and helps to get people thinking about what is different between different kinds of
computing devices an what is really the same. People have good reasons – functional, economic,
esthetic – for choosing one kind over others but underneath the hardware that does the computing
is very similar. The choice is often made because of the network effect: the more other people use
something, the more useful it will be for you, roughly in proportion to how many others there are.
1.1 Logical Construction
An abstract picture of what’s in a simple generic computer looks like the next figure: a processor (the
CPU), some primary memory (RAM), some secondary storage (a disk) and a variety of other
components, all connected by a set of wires called a bus that transmits information between them.
The basic organization has been standard since the 1940s. It’s often called the von Neumann
architecture, after John van Neumann, who described it in a 1946 paper. Translated into today’s
terminology, the CPU provides arithmetic and control, the RAM and disk are memory storage, and the
keyboard, mouse and display interact with the human operator.
1.1.1 CPU
The processor or central processing unit (CPU) is the brain. The CPU does arithmetic, moves data
around, and controls the operation of the other components. It has some basic operations that it can
perform but it does so very fast, billions per second. It can decide what operations to perform next
based on the results of previous computations.
, Summary 2023-2024 Jelke de Haan
When buying a computer, the CPU is often described in very difficult terms. What does “2.2 GHz dual-
core Intel Core i7 processor” mean? Intel makes the CPU, “Core i7” is just a marketing term. This
particular processor has two processing units in a single package: “core” has become a synonym for
“processor”. It is, however, sufficient to think of the combination as the CPU, no matter how many
cores it has. “2.2 GHz” is the interesting part. CPU speed is measured in terms of the number of
operations or instructions or parts thereof that it can do in a second. It uses an internal clock to step
through its basic operations. One measure of speed is the number of such ticks per second. One tick
per second is called one hertz (Hz), after Heinrich Hertz. Computers today typically run in the billions
of hertz, or gigahertz (GHz), so 2.2 GHz means 2.200.200.000 ticks per second. The human heartbeat
is almost 100.000 beats per day.
1.1.2 RAM
The primary memory or random access memory (RAM) stores information that is in active use by the
processor and other parts of the computer. Its contents can be changed by the CPU. The RAM stores
the data that de CPU is currently working on, and the instructions that tell the CPU what to do with
the data. This is important: by loading different instructions into memory, we can make the CPU do a
different computation. This makes the stored-program computer a general-purpose device.
RAM is called random access because the CPU can access the information stored at any place
within it as quickly as in any other. When you have to run all the data until you get to the data you
need is called sequential access. Most RAM is volatile: its contents disappear if the power is turned
off, and all this currently active information is lost.
Every computer has a fixed amount of RAM. Capacity is measured in bytes, where a byte is an
amount of memory that’s big enough to hold a single character. More RAM usually translates into
faster computing, since there’s never enough for all the programs that want to use it at the same time,
and it takes time to move parts of an unused program out to make room for something new.
1.1.3 Disks and other secondary storage
Secondary storage holds information even when the power is turned off, it’s non-volatile. There are
two main kinds of secondary storage:
1. The magnetic disk, usually called the hard disk or hard drive:
Magnetic disks store information by setting the direction of magnetization of tiny
regions of magnetic material on rotating surfaces. Data is stored in concentric tracks that are
read an written by a sensor that moves from track to track. Disk space is about 100 times
cheaper per byte than RAM, but accessing information is slower. It takes about ten
milliseconds for the disk drive to access any particular track on the surface; data is then
transferred at roughly 100 MB per second.
2. Flash memory, often called solid state disk:
More and more laptops have solid state disks which use flash memory instead of
rotating machinery. Flash memory is non-volatile; information is stored as electric charges in
circuitry that maintains the charge in individual circuit elements without using any power.
Stored charges can be read, erased and overwritten with new values. Flash memory is faster,
lighter, more reliable and requires less power than conventional disk storage. A typical laptop
disk holds perhaps 500 GB and external drives that can be plugged in to a USB socket have
capacities in the multi-terabyte (TB) range.
A disk is a good example of the difference between logical structure and physical implementation.
Hardware in the disk itself and software in the operating system create the organizational structure.
The logical organization is so well matched to people that other devices provide the same organization
even though they use different physical implementation to achieve it. The data on a disk could be
stored on rotating machinery, integrated circuits with no moving parts, or something else entirely. An
idea in computing is abstraction: physical implementation details are hidden.
, Summary 2023-2024 Jelke de Haan
1.1.4 Et cetera
A lot of other devices serve special functions. Mice, keyboards, touch screens, microphones, cameras
and scanners all allow users to provide input. Displays, printers and speakers output to users.
Networking components communicate with other computers. They are not connected by one bus, but
there are multiple buses inside a computer, with properties appropriate to their function. The
Universal Serial Bus (USB) is an example of a bus that makes an appearance outside of the computer
as well.
All of these devices have gone through the same evolution as processors, memory and disks: the
physical properties have changed rapidly, towards more capabilities in a smaller package at a lower
price. They are also converging into a single one; a cell phone consist of many devices (cameras,
watches, etc.). A smartphone has the same abstract architecture as a laptop, though with major
implementation differences due to size and power constraints. Phones don’t have hard disks, but they
do have flash memory to store information when the phone is turned off. The external devices are
mostly only Bluetooth, a socket for headphones, an external microphone and a USB connector.
1.2 Physical Construction
Physical construction barely changes over time. For example, an SD card or a laptop disk from a decade
old are likely to look the same as one from today, but the capacity is much higher and the price is lower.
There’s a clear progression in the circuits boards that hold the components of a computer:
there are fewer components today because more of the circuitry is inside them, the wiring is finer and
the connecting pins are more numerous and much closer together.
Electronic circuits in computers are built from large numbers of a handful of basic elements. The most
important of these is the logic gate, which computes a single output value based on one or two input
values; it uses input signals like voltage or current to control an output signal, also voltage or current.
Given enough of such gates connected in the right way, it’s possible to perform any kind of
computation.
The fundamental circuit element is the transistor. In a computer, a transistor is a device that
can turn a current on or off under the control of a voltage. Logic gates used to be built from discrete-
components (vacuum tubes and individual transistors).
Logic gates are created on integrated circuits (ICs), often called chips or microchips. An IC has
all the components and wiring of an electronic circuit on a single flat surface that is manufactured by
a complex sequence of optical en chemical processes to produce a circuit that has no discrete pieces
and no conventional wires. ICs are much smaller and more robust than discrete-component circuitry.
Chips are fabricated on circular wafers about 30 cm in diameter; they are sliced into separate chips. A
typical chip is mounted in a larger package with pins that connect it to the rest of the system.
Gordon Moore observed in 1965 that as technology improved, the number of transistors that could
be manufactured on an integrated circuit of a particular size was doubling approximately every year, a
rate that he later revised to every two years. This meant that computing power was doubling every
two years, if not faster. This exponential growth, now known as Moore’s Law, has been going on for
over fifty years, so integrated circuits now have well over a million times as many transistors as they
did in 1965.
